"Veil." PREYS, eighth episode, first season. The hour-long weekly drama follows a team of scientists investigating a newly evolved species of man. James Morrison plays Lewis, a "Mentor" who trains members of his race in terrorist tactics.

Thanks to Lewis's false report implicating his former student Tom Daniels in a score of murders, Tom and Dr. Sloan Parker hide out among the shadows far away from the city. Sloan, posing as a runaway wife at Tom's suggestion, checks them into a small motel.

Dr. Ed Tate attends the visitation for Kelly, the young runaway whose captivity under the new species apparently led to her illness and subsequent death. Kelly's parents, grateful to Ed for all his help toward their daughter, report the medical examiner could find no cause of her death. Ed swears he will find what killed her. When he pays his respects to Kelly, he sees a lump moving under the skin of her neck.

The next morning, Sloan wakes up with a start in the motel bed. Tom is asleep slouched in an upholstered chair. When she covers him with a blanket, he jerks awake. He tells he wasn't sleeping but thinking about Lewis. Sloan says she can't figure out why Lewis shot Lisa instead of them when he had the chance. Tom tells her Lewis is "toying" with them.

Ed corners his boss Dr. Walter Attwood at the lab and demands they do an autopsy of Kelly. He tells Attwood he saw something moving under her skin. Attwood believes what Ed saw is the result of the depth of his grief for Kelly. Ed reminds him that her illness was the result of her contact with the new species. Attwood tells him to get Kelly's parents' consent.

In the shabby hotel room, Sloan reads a newspaper with their photos and a story detailing their alleged offenses. The police only want her for harboring a fugitive, she says, but they want Tom for murdering 26 people. Knowing Tom used to be an assassin for the new species and that Lewis, the source of that number, was his boss, Sloan asks if the total is true. Tom hesitates before saying that he only killed 5 people because he was programmed to do so. Remembering he was originally assigned to kill her, she asks if she had been the first target he hadn't killed. About a week before he met Sloan, Tom says, he had been assigned to kill a teenage boy. His mother had begged Tom to kill her instead. Sloan asks how Lewis reacted to Tom's apparent failure. Tom says he never told Lewis the truth.

Ed visits Kelly's parents to get permission to perform another autopsy. Her parents hesitate because she has been through so much, but Ed tells them another autopsy is their best chance for getting to those responsible for her death.

In the hotel, Sloan gathers the debris from their dinner of Chinese takeout. She turns on the TV, but Tom says he's not in the mood to see himself on news bulletins anymore. She suggests they watch a sitcom, but he tells her he's not in the mood to laugh. Sloan observes she has never heard him laugh and wonders if he has a sense of humor. To see if he does, she tells him a joke.

While Sloan and Tom relax as much as they can in hiding, Lewis sits in a parked car outside. Over his cell phone and with a sly smile, he reports their whereabouts to the police.

Tom and Sloan settle in for another night. Feeling guilty about taking the bed alone, she declares her intent to share. Although they banter, Tom is clearly uncomfortable being under the covers with her. She thanks him for trusting her enough to tell her about the teenage boy and says she does not judge him. After she tells him "who you are can make it right," Tom kisses her. In mid embrace, Tom realizes the police are coming. She tells him to leave, even though he is reluctant to leave her alone. As he escapes, officers handcuff Sloan.

Former police detective Ray Peterson, who now works for Attwood and his government contacts, visits Sloan in jail. Ray tells her she will have to go through courtroom proceedings and that the cops will plan to have her tailed after she's released so they can get to Tom. Ray questions Tom's motives for having left Sloan to the cops.

Ed and Attwood conduct the autopsy on Kelly's remains. They begin the examination in her neck, where Ed saw movement. They find nothing. Since the lump had been traveling up her neck, Attwood suggests they perform a CAT scan on her head.

Ray takes Sloan back to her apartment. He tells her Tom might try to contact her and that her house is being watched. Unbeknownst to Ray, the police are not the only ones watching Sloan's apartment. Lewis sits outside the apartment in his parked car. He sees Ray leave and then glances in the car mirror to watch the cops parked down the street.

The CT scan turns up something in Kelly's eustachian tube, a canal leading up to her inner ear. Attwood remarks that the object behaves like a parasite. Ed adds, a parasite whose host just died. They conclude that it's seeking a way out.

Sloan's doorbell rings. Her security camera shows a woman who says Tom sent her and quotes the punch line of the joke Sloan had told him in the hotel room. Tom wants her to meet him in Centennial Park at midnight.

Ray picks up Sloan to take her to the park and lose the detectives following her along the way. The cops chase them through empty late-night city streets. Ray loses them and drives on to the park. He offers to stay with Sloan who does not want Tom scared away.

At the lab, Ed pulls a live tick from inside Kelly's ear.

In the park, Sloan waits for Tom. A gang of youths strides past her, as do several men walking alone. She leaves.

Ed has learned the tick has the same DNA differential as the new species does. Not long before her death, Ed had tested Kelly's blood and found her DNA differential was between her human ancestry and that of the new species. As he has suspected all along, Ed believes serial killer and new species member Randall Lynch planted the tick inside Kelly while she was his captive in the cave. Attwood speculates that the new species is using the tick to insert the new species DNA into humans. Ed wants to study the bug through an autopsy, but Attwood suggests they plant it into a living subject.

Sloan returns to her apartment and checks her answering machine. On her only message, a nervous Ed begs her to come into the lab. He does not tell her his fears that Lewis, when he had kidnapped Sloan, had injected her with the new DNA, too. But Tom is waiting for her. He apologizes for luring her to the park and making her wait, but he had intended to get the cops away from her house for a while. He also apologizes for leaving her alone at the hotel, but the phone rings. Sloan answers it because she is expecting the call to be from Ed, but the caller turns out to be Lewis. She demands to know why he set them up as fugitives when Tom grabs the phone from her.

Lewis sits in the car parked outside. "Tom, listen," Lewis says, "We shall reign in the kingdom of man." Tom freezes, as if he is a sleeper agent who has just heard the code phrase. Sloan has no idea what Lewis has said to Tom or any indication why he has reacted so. Tom replaces the phone, pushes Sloan aside and goes outside to meet Lewis. Without a word to each other, Tom gets into the car and Lewis drives away. The detectives watching the apartment are slumped dead inside their car.

Sloan insists to Attwood and Ed that Tom is not responsible for his actions. Lewis had given him some kind of code word planted in his subconscious, Sloan argues. Attwood suggests they prepare for Tom's eventual attack and assassination attempt.

In a white room, Lewis has injected Tom with a mysterious substance with the massive needle he received from the mysterious man in the alley.

Ed wants to insert the tick into a laboratory monkey and see what happens. Attwood tells him watching the results would take time they don't have, so he already injected the monkey with a synthesized version of the substance. Sloan and Tom glance over to the monkey cage to see a group of monkeys bunched together in a top corner, as if they want to get away from something.

In a white room with no doors and no windows, Lewis circles Tom, who is seated in a chair. "It's good to have you back, Tom." An impassive and blankly staring Tom agrees it is good to be back. "Do you think you're ready to get back to work?"

Tom asks what to do. His mother tells him he'll do what he was trained to do. Tom says he doesn't remember. His mother acknowledges it has been a long time. A hallucinated image of Sloan tells him she will help.

Ed and Sloan take blood from James the monkey, the one injected with the active substance believed to be what will change its DNA. Ed remarks they are "on the front lines of biological warfare" and fears many people will die. Sloan says that will not happen if they do their jobs.

After eating Chinese takeout, Ed grills Sloan about her feelings and what he considers her misdirected trust in Tom. He challenges her as to whether she and Tom have had a physical relationship. Irate at first, Sloan says all that happened was a kiss. Shocked from a combination of jealousy and fear that she will share the same fate as Kelly, Ed tells her they have no idea how the new species inserts its DNA into humans. That attack, he says, could be a kiss. Ed's pager goes off, telling him the DNA test on James the monkey's blood is ready.

Still in the white room without obvious walls, Tom thinks Ed is lunching with him and telling him to kill Sloan, that his relationship with her is "dragging him down." Tom agrees. Instead of Ed, of course, Lewis is the one ordering Tom to kill Sloan.

Ed and Sloan are shocked to learn the monkey's DNA differential is the same is the new species after only a few hours of exposure. Kelly's differential had not been that high when she died. After the test, when they walk through the lab, they hear no monkeys screeching. When they check the cage, all the monkeys are dead but one. James swings triumphantly on the cage bars above them.

No longer in the white room, but a small bedroom, Tom wakes up. Lewis sits in a chair beside the bed. After checking on how Tom feels, Lewis tells him, "There's something I want you to do for me, Tom. There's someone in the other room." He hands Tom a pistol. "I want you to kill them."