When the body of a young woman is found, the Chicago police realize there's a serial killer at large after comparing her case with others.

Mulder and Scully track a legendary creature that has roamed the New Jersey countryside for over 40 years.

Cassie and Captain James race to find Cordell, but the situation goes from bad to worse when Liam also disappears; Stella and August pursue a lead of their own.

The Walker family future looks hopeful – until Cordell vanishes. As mysterious captors try to physically and mentally break him, Captain James, Cassie and other Rangers strive to rescue Cordell, but Stella has her own ideas about …

Kelly Severide of Firehouse 51 is brought to the District for questioning when his car is found to have caused a deadly crash, so the team tracks down a group of carjackers that may prove Severide's innocence.

Dawson and Casey meet Louie's biological father. In other events, Severide falls back into old habits as he tries to help Anna with a bone marrow procedure, and Brett opens up to Dawson.

Casey and Dawson apply for permanent adoption of Louie. Jeff Clarke gives Severide an interesting proposition. Otis convinces Herrmann to throw a bash celebrating the 100th anniversary of Molly's, but there are complications.

When Gale comes clean to Geri about the past, Cordell is forced to relive a part of his he'd buried long ago. Trey contemplates Captain James' latest offer.

Gabriela and Antonio's parents come to Chicago for their anniversary, while Chief Boden discovers a secret about his stepson.

A shared vision brings Michaela and Kyle together for a heartbreaking reason. Meanwhile, Eagan offers Ben valuable information – but at a price.