It's 1929, and the TARDIS crew is holidaying in Antibes. While the Doctor practises his painting, Romana attempts to fend off the playful advances of young Tommy Creighton. All is peaceful and idyllic except for the portentous warning of astrologer Madame Arcana, and the fact that personal items are being stolen from the hotel's guests.What is the secret of the cave on the beach? And why do some of Romana's new acquaintances suddenly behave so strangely? As her newfound socialite existence suddenly takes a turn into danger, Romana finds that the whole planet Earth is faced with a deadly threat...
According to the Doctor and Romana, there has been no unusual stellar activity in Earth's part of the galactic quadrant since the Great Comet of 1800. The comet appeared over Antibes in that year. The local peasants believed that it foretold of the end of the world.
Tommy Creighton is attracted to Romana but she is uninterested. Similarly, Madame Arcana is attracted to the Doctor. However, he tells Romana that she is "much too young for [him]."
The Stealers from Saiph is told, like a few other entries in the Companion Chronicles series, in a mixture of first person and third person limited narrative. That is, Romana is recollecting her personal past, and cannot tell more than what she has personally perceived, but she often employs third person pronouns (he, she, they) to tell her story. This narrative style, akin to that of a diary, is somewhat unusual for a Companion Chronicle, but certainly not unique. For instance, The Time Vampire, and the rest of Nigel Fairs' Leela trilogy, employ the same narrative style. A practical result of this style is that the actor is acting through the lens of the primary character. Mary Tamm is therefore not portraying other characters in the story, but rather she is always playing Romana, who is then recollecting the other characters. It is thus possible to explain any perceived inaccuracy of impersonation. Because Romana is not herself an actor or a gifted mimic, "spot on" accents or impersonations should not be rendered. The listener should always be able to hear the voice of Romana, even when, say, the Doctor is speaking.