Dr. Wilfred Glendon returns to London with a rare flower he sought and discovered in Tibet. He also returns with the bite of a werewolf, which causes him to change into one himself during a full moon. Only the juice from his new flower can provide a temporary antidote. But the disease puts a strain on his relationship with his wife; worse, she's still in love with her old beau. Meanwhile, the flower has attracted the attention of the mysterious Dr. Yogami from Tibet.