Detective Murdoch investigates the death of a young man, Nathan Siebold, who died just after prayers at his synagogue. Dr. Ogden concludes that he died of as a result of a consistent and lengthy exposure to arsenic. Nathan worked for Isaac Begelman and there was obviously an attachment between him and Begelman's daughter Devra. She however had another suitor in the form of Dr. Simon Goldberg. As Murdoch delves into the case, he comes to believe that Devra was forcibly being kept away from Nathan against her will but she too is suffering from arsenic poisoning. When a friend of Nathan's is severely beaten, the case begins to make sense and sends Murdoch down a different line of inquiry.