Suspended from her normal duty, Officer Kate Benson is recruited by Special Unit Two (SU2) for a temporary assignment. Mature gargoyles that have been hibernating (on churches in Europe) have awoken and are collecting food (people) to feed to their eggs which have been incubating for 17 years. The victims are being kept alive until the eggs hatch. SU2 has 24 hours to track down the gargoyles and destroy the nest before the mass hatching occurs.
Werewolves, scientifically known as lycanthhropes, (thropes) are roaming the city killing innocent people who just happen to be in the wrong place at the wrong time. But these Links' superhuman senses and strength, and their ability to blend in with the human population while not in wolf form, make the detectives' work quite intense...
On the way to an exhibit at the museum, a mummy is revived by an electrical storm. However, this is no ordinary mummy, it was the most feared Japanese Samurai warrior that ever lived. The mummy wants all the things promised to him in the afterlife. To achieve this the mummy must collect everything he was entombed with, including three female concubines. He has the first two women and targets Kate as the third. For Nick, what started out as a standard Link investigation now becomes a rescue mission.
A Link is formed out of fat from liposuction patients from a plastic surgery clinic. The link kills the plastic surgeon when he gets in the way of the link's food supply and then disappears into the Chicago water system. The first detective on the scene is Rich Talridge, who was O'Malley's first partner before Nick was picked for SU2. Rich doesn't like that the case has been handed over to SU2 and tries to solve it himself which gets him in trouble. Kate and Nick and the rest of SU2 are left trying to track and get rid of the "Fat Link" before it kills again.
Some water Links, nicknamed Mermen, from two years ago have reappeared and are victimizing young women. The merman emits a high pitched sound which temporarily paralyzes the victim thus making it where the merman can empty the victim of their soul. This leaves the victim in a semi-vegetative state. The catch is that it only works on virgins. A tie-in to the story is that Kate's younger sister is visiting and dating a rather mysterious guy. Kate starts to suspect the guy may also be a merman and that her sister may be the next victim.
A Sandman Link takes over the bodies of everyday people when they sleep and has them act out their wildest subconscious fantasies. Kate falls asleep while quarantining an area and the Sandman enters her. Kate becomes dangerous under the Sandman's attraction and the team must destroy it before it's too late for Kate.
A fabulously wealthy - and beautiful - cosmetics executive is Nick and Kate's key suspect after a 19-year-old male model is found mysteriously dead of old age. Using Nick as bait, the SU2 detectives must prove the glamorous tycoon is a witch who has lived for centuries by literally sucking the youth out of her victims to keep herself young.
A Link so monumentally evil that his name has been lost to history reappears on Halloween, the one night of the year when Links can roam with impunity. The confrontation between the Link and Nick is made all the more personal - and lethal - as it is the villain responsible for the death of Nick's former partner. The mysterious Link is bringing the corpses of serial killers back to life so they can carry out his plan to assume leadership of all Links.
Cajoled by Nick into attending her high school reunion, Kate is forced to relive the humiliation of how she ruined her graduation 10 years earlier by taking over the ceremony and hysterically insisting that Links lived in the walls of the school. Acting as her escort to the reunion, Nick helps Kate redeem her reputation when the Links return and attempt to massacre her classmates.
The Scarecrow, a particularly noxious Link, is inadvertently unearthed and loves nothing more than the fear and mayhem he creates by reading - and exploiting - the "fear center" in every Chicagoan's subconscious. As the city degenerates into mass hysteria, Nick and Kate learn that to defeat the Scarecrow, they must first deal with all their own fears and phobias
When Cupid's 'love potion' causes a hangin' judge to start setting high-end criminals free, it's up to Kate and Carl to get an on-the-lam Cupid back to Chicago to reverse his potion's' effect on both the judge and a transformed Nick, whose newfound propensity for seeing the good in everyone begins to wear thin on his colleagues.