A secret Chicago police unit battles paranormal creatures. First up: a young cop joins the squad after witnessing a gargoyle abduct a child. Partnered with the cynical Nick O'Malley, she allows herself to be used as a decoy in an attempt to catch the creature, which is kidnapping prey to use to feed its new batch of eggs when they hatch in the thousands and swarm the city.
Nick finds an unusual way of taking a bite out of crime when SU2 discovers that a pack of stockbrokers-turned-werewolves are terrorizing the city. Nick must get himself infected and go undercover to infiltrate the pack before they go on a rampage, but he may be in over his head.
An ancient Japanese mummy is awakened by a bolt of lightning, and sets out to recreate a ritual which will give it godlike powers. It needs three concubines to do so and Benson finds herself taken captive by the creature, which plans to sacrifice her and two other women.
A “spider woman” preys on unsuspecting men in Chicago, wooing them into her web before slaying them. But a beautiful witness comes forth, helping Nick to clear the cobwebs from the clues. Problem is, there may be more cobwebs than Nick and Kate were counting on.
While they hunt a Link made up of human fat residue, Nick and Kate deal with Nick's former partner, Rich, who wants in on the case and is willing to do anything it takes, including betraying Nick. To complicate matters, Rich is charged with a murder that the monster committed.
Nick and Kate investigate when “mermen” begin stealing young women's minds. Kate's visiting sister Megan is attracted to a guitar player named nicknamed “Scar," but Kate soon suspects he may be a shape-shifting merman who has plans on Megan.
A parasitic Link causes everyday citizens with no prior record to commit heinous crimes. The team traps it in a bus station but Kate is possessed and the only way to kill the Sandman is to kill its host body.
A shape-shifting Link like the one that murdered Nick's partner is terrorizing the city, but its versatility makes a manhunt difficult. SU2 is forced to consult the original Chameleon, but it has its own agenda.
An ancient Link that sucks the life out of humans is on the prowl in Chicago. However, the primary suspect, a cosmetics executive, catches Nick's eye and makes him doubt her involvement.
A Link known as the Boogeyman is on the prowl collecting heads and following its hunting pattern from seven years ago. Kate and Nick must catch it to save a man on death row who took the rap for one of its earlier murders, and are helped by . his son Jake. Since only children can see the Boogeyman, Jake insists on helping them kill the creature that put his father in jail.
A mysterious unnamed Link is bringing corpses of serial killers back to life as part of his master plan to get Nick to bring him an orb that his dead partner Julie recovered on the day of her death.
Gorgon Links, which are capable of transforming people into stone, run rampant through the city, with Kate's soon-to-be ex-boyfriend one of their possible victims.
The theft of an ancient Native American necklace from an Indian burial ground unleashes a dragon that runs amok throughout Chicago looking for its preferred food source, gnomes. It's up to Carl to do battle with the creature since he killed one before... or so he claims.
An ogre Link, the basis for the legend of Jack the Ripper, is stalking and killing strippers in Chicago. While trying to track it down, Kate must deal with a regular cop who also wants to capture the killer and that she's romantically interested in.
Nick accompanies Kate to her 10-year high-school reunion, where the two find themselves fighting Links intent on massacring her classmates.
Nick and Kate battle the Scarecrow, a Link that creates mayhem by exploiting the fears in every Chicagoan's subconscious. It thrives on fear and plans to create a suitably terrifying event to gain enough fear-energy to become invulnerable.
Kate, Nick, and Carl must track down a Cupid Link, which inadvertently caused a tough judge to start handing down easy sentences. They must bring back the Cupid from Devner and get him to reverse his "love" before the judge frees a major felon, but things get complicated when Nick fails to get his dose of the antidote and becomes a nice, lovable... and totally useless guy.
A mind-control Link uses a local children's TV show to turn kids into zombies who steal for him. To get close to the creature, Nick and Kate force Carl to become a sidekick on the show.
Nick and Kate hunt a Djinn, a “genie”-like Link that is compelled to make people's wishes come true. But if she grants enough wishes, she will gain free will and be able to do whatever she wants, including decimating mankind.