A boy (Radames Pera) walks out of an office to his mom (Lisa Pera) telling her his headache is gone. Dr. Eric Fowler (Robert Foxworth) sees them out then receives a phone call. It seems like a crank call from a guy (Greg Mullavey) claiming to be "wired in" and he's been listening in on the doctor and his patients for months. He rattles off several patients' names to convince Dr. Fowler he is for real He introduces himself as "Cerebus, the hound of Hell". Cerebus is ticked off because Dr. Fowler turned him down as "a poor treatment risk" even though he has a 170 I.Q, Cerebus demands $5000 or he will destroy the doctor and "his sickies". Dr. Fowler strikes back telling Cerebus he will not be threatened or blackmailed but Cerebus is not willing to let "the mistake be buried". The phone rings again but Dr. Fowler leaves the building.
Dr. Fowler notifies Five-O as McGarrett and Che Fong (Harry Endo) tear apart his phone equipment. Che asks if he's noticed any static or any other telltale signs of a tap, which the doctor says no. Che calls the phone company to have a line test done since the equipment is clean. They don't find anything unusual or an "electronic trail," which Che accounts that Cerebus could be smart enough to cover his tracks on the tap. Che then scans the room for bugs because Dr. Fowler reported Cerebus was eavesdropping on patient sessions. Che finds the place is "loaded" and Cerebus comes through the stereo demanding the cops leave immediately. McGarrett tells Dr. Fowler it's his decision and Dr. Fowler seeks McGarrett's advice: "call his bluff". Dr. Fowler agrees then McGarrett tells Che to rip every single one of them out. Cerebus threatens Dr. Fowler will regret that decision.
In the apartment of the mom and boy, Bob, they receive a phone call. It's Cerebus! He claims to be part of Dr. Fowler's medical exchange and has a message for Bob. His mom hands him the phone then Cerebus plays a tape when Dr. Fowler and his mother talked privately about Bob's condition: a terminal, inoperable brain tumor. Bob hangs up and completely freaks out throwing things making his sister scream and worrying his mom.
Dr. Fowler and McGarrett arrive at the hospital where Bob was taken and given some drugs to calm down. Dr. Fowler wants to know what happened with Bob explaining Cerebus didn't say anything but only played tapes. Dr. Fowler tells him they discussed an early diagnosis but the tumor is actually benign with the pills helping the tumor shrink. Dr. Fowler gives him a sedative before leaving with McGarrett. In the hallway, they allow Bob's mom in before Dr. Fowler confesses Bob is indeed terminal and it's one lie he will never regret. McGarrett asks if there is anyone else as vulnerable and pieces together that Cerebus may have Dr. Fowler's clothes bugged. McGarrett silently asks for Dr. Fowler's jacket and finds the bug in the collar. McGarrett then writes a note to tell Dr. Fowler to 'kick us off the case. Kick hard'. Dr. Fowler says he's made up his mind; he has to protect his patients and that McGarrett and Five-O need to "stay away!"
That night at Dr. Fowler's house, he realizes there is no peace from Cerebus as the psycho talks to him through yet another speaker! His wife Carol (Elissa Fontes) asks who he's talking to and Dr. Fowler doesn't know how to explain it.
The next morning at Dr. Fowler's office building, Ben searches the basement. He enters a maintenance room where he meets the man (Michael Morgan) in charge. Asking some questions, Ben notices a board with all the keys for the different rooms and suites. The door to the room is open during the day so anyone can come in and make a duplicate key!
At Five-O, Ben briefs what he found. McGarrett scratches the idea of changing locks lest they have "another Bobby Martinelli incident". They walk in to McGarrett's office where Che reports on the bugging devices: no numbers, they're homemade and "very good". McGarrett tells Chin to find the outlets handling the parts. Che moves on to the body bugs: an effective range of about 2.9 miles. McGarrett goes to the transparent board in an attempt to triangulate Cerebus' position based on Dr. Fowler's home and office. He draws two circles in which Cerebus has to stay in. Danno points out there are a lot of people in the real estate but McGarrett is undeterred. He tells Che to set up a sound tracking station near Dr. Fowler's office and to coordinate with the FCC and the phone company because they need their help. He also wants a button installed where Dr. Fowler can signal them when to tune in. Without tipping off Cerebus, McGarrett tells Ben to pass him a note to keep him on the line as long as possible and not to antagonize him. They leave for their tasks.
In his office, Dr. Fowler sees a patient (Patricia Herman) named Mary. He tells her the imagined diseases are avoidance mechanisms. After reassuring her she is fine, Dr. Fowler sees her out. Big surprise, Cerebus was listening in mocking Mary after she leaves. Dr. Fowler hits the button to allow Che and a technician (Michael Leong) to track down the signal from the lab. Danno calls a direct line to "start things on your end" then gives the conversation his full attention. Dr. Fowler keeps Cerebus on by asking if he had immunity from prosecution and a free psychoanalysis, would he accept it? Cerebus laughs saying he doesn't need the doctor. As a matter of fact, Cerebus wants $10,000 now and gives instructions on where and how to drop it. Meanwhile, the technician has found the coordinates as Danno receives coordinates from the FCC. Danno then calls HPD to order roadblocks on the canal "corner of Ala Wai and Makali" looking for aerial antennae and tapes as well as arresting all suspects. HPD moves in.
Dr. Fowler meets with Dr. Barnes (Winston Char) at the hospital over his patient Eva Haynes (Linda Ryan) who took a whole bottle of sleeping pills but changed her mind calling an ambulance. Dr. Fowler talks to her, thinking she wouldn't try another suicide attempt. She tells him she couldn't help herself because it would have been Melissa's sixth birthday. Dr. Fowler assures her Melissa died of a condition she was born with and it could have happened anywhere and at anytime. Dr. Fowler leaves her saying he wants to see her all week.
In McGarrett's office, Duke (Herman Wedemeyer) briefs they stopped several people but couldn't book any of them. Duke goes on saying they didn't find any "radio recording equipment" or homemade tapes, only standard tapes for car decks. One thing in their favor, photos were taken of everyone stopped. Chin tells them he struck out trying to find the components because they're sold at "electronic supermarkets" and many of the parts are in open bins. The stores don't keep track of their customers and what couldn't be bought, could be stolen. McGarrett knows they need more; he turns to Danno about Dr. Fowler's patients. He tracked down the angle of a patient with electronic background and came up with three: one is in Japan, one is currently at Edwards Air Force Base, California and the last is dead. Ben suggests the guy could be self-taught. McGarrett wants a face-to-face with Dr. Fowler and asks Duke to play highway patrol to track him down.
Duke pulls over Dr. Fowler on "an unsafe lane change" but really passes him a note from McGarrett asking to meet at Oahu Health Club tomorrow at 1:00 p.m.
The next day, Dr. Fowler goes to the Oahu Health Club with Ben meeting him at the door. Ben shows him his badge asking if he still remembers his way to the locker room and he does. A little while later, Dr. Fowler meets Ben in the parking lot in another set of clothes. Ben drives him away. Later, in McGarrett's office, Dr. Fowler is unable to point out anyone from the roadblock. They discuss Cerebus and who he can possibly be. Dr. Fowler remembers when he and Carol returned from a weekend at the Kuilima Resort, they found a window open at the house and the closet rearranged. McGarrett then asks for his help with the drop and Dr. Fowler agrees.
That night, Cerebus is every which way ticked off because he didn't hear anything from the doctor that afternoon. Cerebus makes it known he's been listening in for a long time, even before the couple's separation due to an affair Dr. Fowler had. Cerebus keeps rubbing salt into the wounds asking about the $10,000. Satisfied with Dr. Fowler's answer, Cerebus tells him to pick it up first thing in the morning and to stay tuned to his car radio.
The next morning, Dr. Fowler arrives at the Bank of Hawaii to retrieve the money. Danno and Che watch Dr. Fowler enter the bank, as Che is setup with tracking equipment in the back seat. Danno checks in with the back up units reminding them to use tactical frequency and voice scrambler. Inside, Dr. Fowler sets the airline bag on the counter asking the teller (Paula Hayashi) about the money he called ahead for. She takes the bag and switches it with one Duke has next to him. Dr. Fowler takes it and leaves pulling away from the bank with three cars following.
On the highway, Dr. Fowler turns on his radio as Danno tells Che about a nearby power plant but the signal is coming in clear. Cerebus is watching through binoculars ordering Dr. Fowler to move into the left lane hugging the rail. Dr. Fowler does this and throws the bag when told over the rail. Meanwhile, Che tracks the bag's movements telling Danno to get off the freeway as the bag is moving northeast. Danno keeps the other units apprised of the movements and the fix they have. Arriving at the spot, Danno, Che and two HPD officers search the area only to find the bag empty of the money. Danno picks it up by a stick to carry it back to the car. From his perch, Cerebus watches through binoculars happily satisfied he outsmarted the cops.
In Dr. Fowler's office, Cerebus screams at Dr. Fowler for going to McGarrett again. He now wants $20,000 but Dr. Fowler is done playing games: he starts calling clients to discontinue treatment, which angers Cerebus even more. He becomes more desperate because he feels Dr. Fowler slipping out of his grip.
Eva paints in her apartment working on a portrait of a mother and her child. Cerebus calls her and taunts her about her daughter's death pushing Eva to verge. Eva throws herself off her apartment balcony.
Ambulance attendants take her body away as McGarrett stands by and Dr. Fowler pulls up. He identifies her as Danno walks up with information from the switchboard operator: they recognized Cerebus' voice as someone calling Eva just before she jumped. Dr. Fowler is beyond frustrated because he warned her. McGarrett writes a note to go to his office so they can debug Dr. Fowler. He refuses, "I want out," before getting in his car and driving away. McGarrett tells Danno he isn't out and they aren't either.
Dr. Fowler packs his office when Cerebus calls again telling Dr. Fowler to call back his patients for a full schedule tomorrow. Dr. Fowler refuses, slapping the button to notify Five-O Cerebus is communicating. Chin listens in at the lab.
Later, Danno arrives dropping a suitcase in the outer office of Dr. Fowler's suite. He walks out with Mary as she talks about wanting to die and how she tells herself every day. Dr. Fowler takes the suitcase into his office as the phone rings but it's Paul (John Hunt), another doctor who just ran a routine physical on Mary. He warns Dr. Fowler Mary could suffer a massive coronary but Dr. Fowler doesn't want to discuss it over the phone and abruptly hangs up leaving Paul perplexed. Dr. Fowler opens the suitcase that has a list of instructions in it for him to follow. Dr. Fowler completes each of the steps meeting McGarrett and Danno outside. McGarrett tells him Cerebus has to be within 2.9 miles of him in order to eavesdrop. Danno asks if he knows anyone in the "boonies" and he does. McGarrett and Danno leave to set up a consultation between Dr. Emmett at North Shore Valley Hospital.
Dr. Emmett calls Dr. Fowler with Ben standing with Dr. Emmett. Dr. Fowler tells him he'll be there in 40 minutes before calling the exchange to have them cancel all his afternoon appointments and message his wife he's on an emergency.
McGarrett and Danno wait on a road for Dr. Fowler. Chopper Two reports a pair of vehicles near Dr. Fowler's car. McGarrett wants their license plates. Meanwhile, Cerebus calls the hospital to talk to the Chaplin, Father Shay (Don Lev) to find out if "Fred Walsh", the patient Dr. Emmett called about, is real. Father Shay doesn't have a Fred Walsh on his list. Cerebus angrily hangs up the phone.
Dr. Fowler is beyond frustrated but McGarrett explains somehow the Chaplin wasn't notified of the plan. He calls Chin through a patch: McGarrett wants tracing equipment in Mary's apartment because Dr. Fowler suspects Cerebus will go after her next. McGarrett has a new plan and tells Danno and Dr. Fowler to get into the Park Lane. McGarrett pulls into a parking lot and asks them to swap clothes. Once Danno is in Cerebus' range he is not to talk to anyone because he'll be bugged. Then Dr. Fowler will go with McGarrett.
They go to see Mary, where Dr. Fowler informs her of her heart condition. McGarrett reassures her Cerebus might call, they don't know for sure. Suddenly, the phone rings causing Mary to jump out of her skin. Wondering what to do, McGarrett tells her to keep him on the phone as long as possible before running to his car radio. Chin tells McGarrett they're running the trace and hopefully he doesn't move. On the phone, Mary gives Cerebus a bogus story about dropping her needlepoint and being tangled in yarn. She tells him not to go anywhere and after several minutes begins talking to him again. Cerebus plays a tape but rather than her hearing it, it's Dr. Fowler listening in. Chin has a location on the trace: a phone booth at the Kahala Mall. McGarrett backs out of the parking lot to race to the Kahala Mall.
On the way, McGarrett tells Ben and Duke where Cerebus is. He then tells Chin to pick up Dr. Fowler from Mary's apartment because he might be needed. At the mall, Cerebus spots Ben and Duke first and takes off running. They give chase as Ben yells into the walkie-talkie that he's headed for the back of the building. McGarrett drives to the other side. Meanwhile, they chase up and down stairs eventually coming upon a U.S. Mail truck. Looking inside, they find the original cassettes and some pieces to make bugs. He takes off running again only to run into McGarrett on a back street. McGarrett joins the chase pursuing him up a few flights of stairs finally cornering him on a landing. McGarrett punches him once to subdue him. Bringing him downstairs, Cerebus yells at Dr. Fowler vowing revenge before spitting on him. Dr. Fowler says the right hook made him feel better. McGarrett muses about the inability to cure psychotics with right hooks.
This plot summary Copyright Bobbi Baker ©2019. No reproduction of any kind without permission.