Herbie and Violet's fifth gripping adventure brings the internationally bestselling Eerie-on-Sea series to a heart-stopping climax. It is midwinter once again, and the hosts of a paranormal podcast have descended on Eerie-on-Sea eager for a sighting of the legendary malamander. Herbert Lemon, Lost-and-Founder at the Grand Nautilus Hotel, is feeling uneasy - and not just because of the visitors. He's being plagued by unsettling dreams, and the head-splitting 'Eerie Hum' that is reverberating through the town. Something is dreadfully wrong, and it seems to be coming from Eerie's very core. Herbie and his friend Violet Parma will need all their courage as they head deep below the town to seek answers. Perhaps here, finally, they - and the malamander too - will discover the Deepest Secret of Eerie-on-Sea.