When a dead body is found clutching a 300-year-old finger bone, Booth and Brennan's investigation leads them to a dive site off the coast of Assateague Island where a pirate treasure may be buried. Hodgins is excited to get out of the lab and participates in a dive that uncovers more skeletal remains, which are authentic but prove that some of the bones found were actually stolen from the Jeffersonian collection. The investigation uncovers the possibility that the skeletal remains were placed at the dive site by a surprising culprit with a selfish motivation. But when the suspect is found murdered, a new lead sends the duo on the search for the owner of the dig shaft. Hodgins, excited to get involved in the case, volunteers for another dive in the shaft, but Brennan and Booth must race to save him from an underwater death when they discover who's behind it all.