Paul Schackman

Afraid they will never get pregnant, Lily and Marshall decide to see a specialist; Robin begins her new job.

Lily and Marshall receive shocking news that has a profound impact on the gang; Ted begins his duties as best man for an old friend's wedding.

When the body of a half-naked woman is found hanging by cuffs in a public park; the investigation takes Castle and Beckett into New York's underground world of sexual domination.

Following an injury in the aftermath of an industrial fire, Severide and Seager work together to investigate an anonymous tip. Kidd searches for the right person to fill the open spot on Truck 81. A possible new recruit to 51 gets tested at a call.

Conrad goes head-to-head with Bell after he recommends a risky medical device; Nic fears Conrad is getting overly attached to a patient; Mina and Austin grow closer while working on a difficult heart transplant; Devon embarks on a very difficult day.

In an attempt to save the world, the team searches for Gravitonium.