After Alisha was tragically murdered in last season's final episode, and Simon traveled back in time to when he sacrificed his life to save hers, Curtis and Rudy continue their community service. Seth returns to pick up Kelly's belongings, as they have decided to move to Africa after a visit where Kelly realized she could use her power to deconstruct land mines. Two new offenders join the community service team: Jess, who has X-ray vision, and Finn, who is a telekinetic. The new offenders quickly realize something is not right. Rudy, Curtis, and Seth (and eventually Jess and Finn), have been infected with some sort of virus after a badly hurt man, with a briefcase handcuffed to him, stumbles into the community center and collapses at their feet. The group becomes so obsessed with obtaining the briefcase, that they're ready to murder each other over it. Finally, as the group tries to get the briefcase from Finn on the roof, the hurt man lunges for it and falls to his death, ending the virus. The new probation officer finally arrives, and is creepy and, possibly psychotic. Finn goes home, and we see that he has a girl bound and gagged in his flat.
- After Alisha's death and Simon's departure to the past, Kelly and Seth travel to Africa, where Kelly uses her knowledge of mechanical systems to defuse land mines, and end up staying. Curtis and Rudy continue with community service joined by Finn, an anxious telekinetic, and Jess, a snarky, reserved girl with x-ray vision. Major subplots include Rudy and Finn moving into the community centre together, Finn's one-sided infatuation with Jess, Curtis's encounters with Lola, a mysterious woman who claims to be a trainee probation worker, Finn's search for his father, and Jess's relationship with Alex, "From the Bar", a mysterious bartender who spends most of his time looking for his penis, lost as a result of a mysterious power. As a result of his encounters with Lola, Curtis ends up using his resurrection power again, leading to his own infection. In order to stop his increasing thirst for blood, Curtis commits suicide, emotionally affecting Rudy as a result.
After Curtis's suicide, the gang encounters Abbey, a girl who suffers from amnesia as a result of the storm who later joins the group on community service, and Nadine, a nun with a mysterious secret whom Rudy falls in love with. Alex finds and retrieves his penis, but his regained sense of masculinity causes him to cheat on Jess, angering Finn. Nadine's power is eventually revealed to be the ability to inadvertently summon the Four Horsemen of the Apocalypse when surrounded by anger or violence, which she does after witnessing Alex and Finn arguing over Jess. The Horsemen attack the gang and stab Alex when he steps in to protect Jess. Nadine sacrifices herself in order to stop the Horsemen from wreaking more havoc, leaving Rudy heartbroken once more. As a result of the Horsemen's attack, Alex is rushed to the hospital to receive an emergency lung transplant.