Booth asks Brennan to help locate and identify the remains of a six-year-old boy, Charlie, who went missing from a local park.

Brennan and Booth stumble upon a subterranean world of homeless people when they find the remains of a filmmaker in the ventilation shaft of an underground tunnel.

The team helps Deputy Director Sam Cullen's daughter, Amy, when she contracts a rare form of lung cancer after receiving a bone graft. Booth and Brennan learn she is not the only victim with this rare form of cancer.