 In this engaging costume melodrama of skulduggery on the low seas set back in the 18th-century, the Royal Crown suspects a bit of smuggling is going on in this locale, and they send Captain Collier (Patrick Allen) and his crew to check it out. As the Captain gets into his investigation, mysterious swamp phantoms cloud up the real issue which seems plain enough to see. Captain Collier suspects that the odd village vicar (Peter Cushing) might be hiding something, and what better way to do that than by fortuitous ghosts to scare away the curious, or by posing as someone he is not?