It’s the mid-19th century, and HMS Asp is on a routine mission charting the British coastline for the Royal Navy. But strange sounds and a ghostly apparition unsettle the crew, far away from the safety of shore. As fear spreads among the men whispers of a haunting take hold.

Is this the strain of isolation playing tricks on the mind? Do the crew have cabin fever - or could someone, or something, be moving below decks?

Danny Robins investigates, with Evelyn Hollow and Dr Ciaràn O'Keeffe.

Presented by Danny Robins

Experts: Evelyn Hollow and Dr Ciaran O’KeeffeStory sections by Victoria LloydResearch by Nancy Bottomley and John WestFilming and editing by Robb LeechEditing and sound design by Charlie Brandon-KingTheme music by Katherine PriddyTheme co-produced by Jennifer Ann KellerIncidental music by Evelyn SykesCommissioning executive: Paula McDonnellCommissioning editor: Rhian RobertsProduced by Simon Barnard and Victoria Lloyd

A Bafflegab and Uncanny Media production for BBC Radio 4