In The Case of the Haunted Island, Captain Hay was a Scot who bought over the schooner Mahina from Captain Nathaniel Clark. After discovering the murder of Captain David MacDonald, Biggles and Marcel sought out the Mahina and found it at Tongariva in the Paumotus in the possession of Hay. Hay told them that Clark had sold the Mahina to him and planned to return to England. Along with the ship, Clark bought over forty tons of canned goods (the stolen cargo from the Belinda) as well as a sextant and a chronometer with the initials "D.M.". Clark had also tried to sell him a gold watch with the full name of the murder victim "David MacDonald" inscribed on it. Biggles told him the instruments and cargo had been stolen from the Belinda and that Clark had murdered MacDonald. The instruments had to be surrendered as evidence but Biggles advised Hay to sell the cargo, keeping an account of the sales as it would have gone for salvage. Realising that he had been duped, Hay signed a statement for Biggles which was later used to help convict Clark.