Barbara Shelley returns to her unhappy childhood home upon request of her creepy uncle, unfaithful husband and self-involved friends in tow. There dear uncle informs her that the family is cursed to become were-leopards, and she is next in line to start transforming.
A rather obscure film that still hasn't been released on DVD and has only rarely been shown on TV. Unfortunately, it just isn't very good, though deserving of some kudos for trying to create psychological atmosphere before throwing in the towel and devolving into a typical AIP monster film. A very young Shelley is good in an early horror role, and rises above the material (her leopard outfit is particularly silly), but the rest of the cast are all undeveloped and disagreeable, especially the jerk of a doctor who is supposedly trying to help her. Without trying to give anything away, I can only say that I doubt anyone would be satisfied with the film's ending.
As has often been pointed out, this is a sort of British answer to Cat People, but is actually closer to The Leopard Man than anything. Still not very good, though. Probably it's only lasting worth is the gateway it gave Barbara Shelley to the world of horror films, much to many a fan's delight.
Note: The British version runs some six minutes longer than the US one, a fact made obvious by the many fades to black present in the AIP version.