US Airdate : 27 October 2003
UK Airdate : 11 June 2004

Hector Freimark (David Hewlett) approaches nightclub owner Milo Dinovi (Salvatore Migliore) at the bar and hands him a small vial of a drug. When Hector leaves, Milo greets Lexa (Karen Cliche) warmly and leads her to a table. Jesse (Forbes March), who is hiding at the bar, watches as Lexa shows Milo a photograph of her brother, who Milo confirms was in the club recently. When Lexa isn't looking, Milo pours the drug into both of their cocktails. After finishing their drinks, Milo gets an immediate high, but Lexa starts to have a violent reaction and Jesse races over and catches her as she falls out of her chair. He then grabs Milo and demands to know what he gave Lexa, but two bouncers restrain him. Lexa suddenly comes to and shoots lasers from her hands at one of the bouncers. She then kicks the bouncers into the bar, before collapsing.

At Lexa's request, Jesse takes her to see Dr. Marcus (Gary Farmer). When he comlinks Brennan (Victor Webster) and Shalimar (Victoria Pratt) to tell them what occurred, Brennan races to the club. Dr. Marcus is able to stabilize Lexa and Jesse goes to meet Brennan. Milo is surprised to see Brennan and Jesse, but refuses to tell them what he gave Lexa. Jesse threatens Milo and he finally reveals it was an upper called DXL. Searching him, Jesse finds two vials of the drug, which he takes. Back at Sanctuary, Shalimar tells Brennan that Dr. Sara Stanton (Jessica Stein), a former Genomex employee, developed DXL to control mutant aggression, but became addicted to the drug. Lexa then enters and informs them that Adam was going to have Sara arrested, but her lab exploded and she disappeared. She just learned, however, that Sara was recently arrested for drug trafficking and tells them that she's going to disguise herself as a transfer prisoner to get to her. The team insists Shalimar go along. Meanwhile, Dr. Marcus tells Jesse there is still DXL in Lexa's system, which will destroy her if an antidote is not found immediately.

Lexa and Shalimar arrive at the prison and are taken and strip-searched. Suddenly Lexa's hand begins to tremble, but she gets it under control. Meanwhile, Jesse and Brennan agree to only tell Shalimar that Lexa could die, afraid that if Lexa were to find out she would kill Sara before they get the antidote. The next morning, Jesse visits Shalimar and tells her about Lexa's condition, insisting only Sara can help. He then phases her a comlink ring and a vial of DXL through the window. Later in the prison work farm, Lexa approaches Sara, but Ruth (Suzanne Coy), another inmate, cuts her off. Ruth then takes a swing at Lexa, but Shalimar grabs her arm stopping her. Back at Sanctuary, Brennan tells Jesse the prison's records show one of Sara's frequent visitors is Hector Freimark, a mutant with whom she was involved with at Genomex who is able to create explosions. Back at the prison, Sara meets with Hector who plants a passionate kiss on her. She pushes him away and demands the DXL. When he tells her he doesn't have it, but that the deal will soon be finalized, she accuses him of double-crossing her.

Later, Lexa and Shalimar approach Sara and tell her they want in on the plan. As an incentive, Shalimar hands Sara the DXL and she greedily pours it under her tongue. Suddenly, Ruth attacks Sara with a knife, but Shalimar leaps in her way as Lexa uses her powers to remove all the light from the room. When the lights come back on, Sara flees the room with Shalimar and Lexa. Sara tells them her boyfriend Hector had hired Ruth to protect her, but he's obviously changed his mind. Lexa promises Sara they can get her out of prison providing she does business with them instead of Hector. She agrees and the team devises a plan to break her out the next day.

That night, Lexa goes to Sara's cell and reveals she's a mutant. Noticing Lexa trembling, Sara tells her the DXL is killing her, but she has an antidote. Feeling betrayed by her team, Lexa returns to her cell and tells Shalimar that she knows she's dying, but Sara will give her the antidote when they break her out. The next morning, Shalimar picks a fight with Ruth in order to distract the guards. Lexa grabs Sara's hand and refracts the light, making them invisible as they walk out of the prison yard. When a guard notices they're missing, they sound the alarm and handcuff Shalimar, believing she is involved. Meanwhile, Brennan and Jesse wait in the Helix for Lexa and Sara to arrive. Jesse uses the comlink to contact Lexa and he and Brennan are stunned when she tells them she's no longer their problem. Suspecting Sara will find Hector, Jesse searches for leads on the computer. Inside the prison, a guard tases a restrained Shalimar, demanding to know where Lexa and Sara are, but she uses her feral strength to break the ropes and knock him out. As she tases the prison matron, a guard rushes in and points a gun at her. Before he can fire, however, Brennan bursts in, slams him against the wall and fires a tesla coil at a second guard. When they join Jesse in the Helix he tells them a large shipment of the chemical needed to produce DXL was recently delivered to a nearby farm.

At the farm, Lexa uses her powers to make her and Sara invisible. Outside the barn, Lexa knocks out one of Hector's guards. Sara snatches his gun while Lexa flickers between visibility and invisibility, struggling to maintain her mutant powers. Suddenly collapsing, Lexa begs Sara for help, but she walks into the barn with the gun surprising Hector. She accuses him of ordering a hit on her in jail, and when he offers her some DXL, she steps toward him, wavering in her anger. Outside, the team finds Lexa's unconscious body. All of a sudden, Hector's men come out and Shalimar attacks them while Brennan drags Lexa to safety and Jesse runs inside. When Jesse enters, Hector grabs the gun from Sara's hand, but she quickly shoves an open brick of DXL into his face. Reacting to the drug, he shoots wildly and hits a nearby tank of CO2 and the supply of DXL. Jesse sees Hector taking one of two needles from a first aid kit and realizing it's the antidote, knocks him down and takes the needles. Hector's fingers start to glow and the barn is soon filled with small explosions. As Jesse runs out, a huge fireball encases the building, destroying both the DXL and its creator. Jesse rushes to Lexa and injects her with the antidote, but when she doesn't respond, he breathes into her mouth and she finally coughs. Jesse takes the other needle and injects himself, halting any effects of the DXL.