A short campaign for Call of Cthulhu set in 1920s Montreal. From the back cover: "This dangerous investigation is set in Canada, in the 1920s. The investigators meet the powerful Lavoie family of Montreal and learn what imperils them, they glimpse a strange cult that now thrives in Quebec and the ancient nemesis that guides it, they come to understand the significance of the corpse discovered in the foundations of a former seminary, they at last perceive the true motives of Father Philip McBride, and they gather at last the full truth about a Churchly saint who has long fascinated McBride. There are plenty of puzzles to solve and investigation to be done up until the final day of play, an unusually complete blend of action, deduction, and interesting situations. Player Characters have time to get their bearings, making this adventure a good one for beginners, but even old hands are soon challenged by a succession of deadly perils. Horror's Heart is designed to be finished over several evenings. It includes about twenty handouts, many illustrations, several new spells and magical traps, and lots of murders and murderers..."