After a bike messenger, carrying a package with content that is able to free a wrongly convicted man from prison, is brutally murdered, Castle and Beckett need to investigate the case. But they are surprised to find out that the tragic death is linked to another murder case previously investigated by Captain Montgomery. Now, in order to solve the new murder, Castle and Beckett must dig deep and discover all the secrets of a prominent New York family.

When a body is found at a sci-fi convention, Castle and Beckett are warped into the heart of fandom -- a world of egotistic celebrities, diehard costumed fans and enough drama for two galaxies.

When Castle and Beckett find giant footprints at the site of a vicious murder, the team is forced to confront the unlikely theory that Bigfoot is the killer. But as they trek into the world of primate research, big game hunting and mythological creatures, they realize that finding the man (or beast) responsible may put them on the endangered species list.