In 18th Century coastal Italy, the local fishermen haul in a gigantic serpent. The Doctor identifies it as an alien, but to the ailing locals this fabled sea creature has the capacity to heal -- if only Count Otto will share it with them. When Mrs. Wibbsey comes under the influence of the Count, the Doctor finds himself snared by the infamous Cagliostro! Set after the Nest Cottage Chronicles, this new story is read by Susan Jameson (Mrs. Wibbsey).