Detective Murdoch investigates the sudden death of bicycle racer Joe Fenton. Murdoch was himself a participant in the race trying out his newfangled gear shifting device but Fenton was the favorite having won several recent races. Fenton's manager, Chippy Blackburn, was seen giving him a potion and they suspect he may be may be fixing races. Dr. Grace however is having considerable difficulty finding a cause of death and with Dr. Ogden's assistance performs her first brain bisection. It leads her to believe he suffered a cerebral aneurysm leading to a brain hemorrhage. The discovery of an injection mark in Fenton's right arm leads to a different conclusion however. Meanwhile, Julia prepares to sell Darcy Garland's house but finds that his younger brother Leslie living is living there.

Detective Murdoch investigates the death of Katie Buchanan who is found dead at the beach, on a hot summer's day, by her friend Elaine Lawson. Both were entrants in a beauty pageant known as the Miss Purity competition, to select the new face of Alexander soap. Dr. Ogden, who is spending her day off at the beach finds what appears to be a large animal bite on the woman's torso. Katie's boyfriend, James Bennett, had recently left her for another competitor, Marie Nicholson and becomes the prime suspect. Inspector Brackenreid however is certain he saw a monster in Lake Ontario and Murdoch is skeptical until he too sees a creature in the water. Constable Crabtree is dismissive of any suggestion that there might be a monster in the water and pursues a more realistic line of inquiry.

Detective Murdoch investigates the murder of Nathan Peters, a ragtime musician and renowned band-leader, who was found dead at the docks. His group, the Jubilee Singers, was performing nearby and his wife had already reported him missing. Dr. Emily Grace determines that he died in the early hours of the morning from a blow to the head causing a subdural hemorrhage. The evidence in the case begins to point to one of the Jubilee Singers as the perpetrator. Much to George Crabtree's chagrin, Emily seems to have taken an interest in the roguish Leslie Garland. Julia meanwhile feels that a huge weight has been taken off her shoulders now that James Gillies is dead.

On his deathbed, Jeffrey Roundhill confesses to having killed his wife Evelyn some 8 years before and tells Murdoch where to find her remains. Dr. Grace confirms the identity of the skeleton as that of Mrs. Roundhill but the manner in which she died doesn't match Roundhill's statement. Further investigation reveals that Roundhill was actually in Winnipeg on the day his wife disappeared. Julia recalls a case, that of Amelia Thompson, who was killed just as Roundhill describes. At the time, Murdoch was convinced that her husband was responsible for his wife's death. Could the two men have killed each other's spouse? Meanwhile, George Crabtree hasn't seen much of Emily lately and takes Leslie Garland to task for interfering in their relationship.

Detective Murdoch and station house 4 employ a con woman to catch an elusive murderess. Doctor Ogden receives a threatening note from beyond the grave, or is it? Doctor Grace and George hit turbulence in their relationship when she is forced to 'ad-lib' during the performance of her life. Was she acting? Murdoch and Julia hit yet another snag in their already complicated relationship. William decides to forge ahead much to Julia's consternation.

Julia, Emily and four of their friends head off to a remote cabin on an island. It's a party to celebrate Lavinda's upcoming wedding to Cedric Maxwell. Cedric's sister is part of the party and she and her brother own the family retreat. Julia is obviously not happy and confides in Emily. Before long however, the women are being killed, one by one. Still reeling from Julia's rejection of his marriage proposal, Murdoch immerses himself in his work. When a drunken Crabtree challenges Leslie Garland to a curling match, he has to put a foursome together. Murdoch declines an invitation to join but applies his scientific approach to helping them play better.

After the assassination of U.S. President William McKinley in Buffalo, Ottawa-based spy Terrance Meyers shows in Toronto. The Canadian government is concerned that some of the assassin's co-conspirators may try to make their way to Canada to avoid U.S. authorities. Rumors have it that Emma Goldman is back in Toronto and the police begin rounding up anyone who might be considered the least bit subversive. Among them is Anton Wocek who is later found dead in a warehouse with Meyers standing by him with the gun in his hand. That's enough for the supremely arrogant American spy Allen Clegg who believes Meyers is part of the conspiracy. Murdoch sets out to prove Meyers' innocence and find out exactly what is going on.

With Murdoch away, Constable Crabtree finds himself investigating the apparent death by poisoning of a visiting Chinese official who was in Toronto seeking men who had participated in the Boxer Rebellion. Their immediate suspect is Wu Chang but as Crabtree gets to know the young man, he is increasingly convinced of his innocence. It turns out it's not Boxers they're after. Murdoch and Julia Ogden meanwhile are trying to find their nemesis, James Gillies. Things take a strange twist when the Cobourg police inform them they may have found Gillies' remains. Ballistics settles the issue but one question remains: who wrote the threatening letters. Murdoch settles that mystery as well.

The police continue their search for Mick and Tim O'Shea but Inspector Brackenreid is also out on his own looking for them. Murdoch finds someone who confirms that the O'Sheas killed Richard Dawkins but the man also suggests that the O'Sheas aren't working alone. Mrs. Cecily McKinnon, the harbor master, says she knows nothing of extortion on the docks but when pressed, points the finger at one of the merchants, Lionel Jeffries. When the O'Sheas are found dead, shot through the head, Brackenreid becomes the number one suspect. Meanwhile, the ladies who participated in the suffragette protest - including Drs. Ogden and Grace - are still in jail. In court, they find that Leslie Garland is one of the Crown attorneys prosecuting them. They get a bit of a boost when Clara Brett Martin, the first woman lawyer so recognized in the British Empire, offers to represent them.

Julia Ogden is invited to dinner at the warden's, only to have a murder take place instead of dessert. Murdoch investigates the murder of Mrs. Hart's friend's fraternity brother.