The crew is hit with an attack by an unknown force unlike anything they've seen before. As confusion and aggression take hold, Marcus and Sam can no longer trust their own senses even as they race to save the sub and defend the island.

Marcus brings the members of the Colorado and the islanders all together to celebrate their two cultures -- a feast in the spirit of Thanksgiving. But the good times turn bad the next morning when an essential crew member is accused of a serious crime. Grace handles the man's defense and is tasked with finding out the truth.