Ben and crew of The North Star uncover a device emitting a strange sound; Ryn finds shelter in the home of the local folklore expert.
The investigation into a museum curator's death takes a bizarre turn when Castle and Beckett learn he is not the first member of a recent archaeological expedition to die.
Maddie rushes to Ryn's rescue after she is taken in for questioning; Ben and Xander return to the deep sea to search for answers, only to be met by an uninvited guest.
The enchanting siren song takes hold of Ben and Decker; Dale must answer for the escalating crime in Bristol Cove.
Buffy and Giles (Sarah Michelle Gellar, Anthony Stewart Head) become suspicious of a Peruvian exchange student (Ara Celi) with whom Xander (Nicholas Brendon) falls in love.
