On a newly christened passenger lake ship to investigate a threat to it, Murdoch must investigate an apparent death of a woman overboard, only to discover a far more complex mystery on board.

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 and many others attend a special showing of a film that will also include sound. The man behind the scheme is James Pendrick and his main competitor, Thomas Edison, is also present for the showing. The film includes a scene where a shot is fired but when the lights come up, one of the patrons, Pendrick's principal investor, has been shot in the head. Thanks to an observation by Dr. Ogden, Murdoch concludes that the shot was intended for Pendrick himself. Pendrick decides to make a film about the cases of Detective Murdoch but in one scene, the actor playing Murdoch is shot by a real bullet. In the original script a character called constable Tom, played by Pendrick, was to be shot again seeming to confirm that Pendrick is the main target. With the investigation ongoing, movie making is proving to be a distraction.

Murdoch finds his investigation into a nanny's disappearance assisted by the man who considers himself the real Sherlock Holmes.

Detective Murdoch investigates the death of Emily Fuller whose body is found on the riverbank. They trace her to her home where her husband Jeremiah is completely impassive. The dead woman's daughter Betty says her father has been like this since he had been away recently for a few days. Dr. Grace determines that Emily did not drown, as they had initially suspected, but was strangled by someone with a very large hand. Constable Crabtree thinks he knows what's happened after he finds that Jeremiah is officially dead - he's now a Haitian zombie, risen from the dead. After Dr. Grace finds that a second victim's brain has been operated on, Murdoch thinks he knows who they are dealing with.

Detective Murdoch investigates the death of Sarah Bosen who apparently threw herself from her hospital room window and breaking her neck in the fall. Sarah was being treated by Julia Ogden for arachnophobia and had been making some progress in overcoming her fears. Murdoch however finds a dead spider in her room. The three remaining members of the treatment group begin to have their doubts about their therapy. Julia's colleague, Dr. Charles Linden, thinks her therapy is a waste of time and as far as he is concerned, Sarah's death proves him correct. He launches a formal complaint to have her research terminated. When her other patients are forced to face their phobias, Murdoch concludes that someone is trying to kill her patients. Meanwhile, Crabtree tries to save his pet spider from Dr. Grace's experiments and Dr. Ogden helps Murdoch overcome his own irrational fear.

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 death of Peter Farrelly who had a loud altercation with someone the night before his body was found. Dr. Grace determines he was beaten to death. She also found chloral hydrate in his system - a bottle of which they found in the victim's luggage. They believe both the victim and his killer are from Newfoundland and so Murdoch and Crabtree head off to St. John's in the hopes of finding the suspected killer Ezekiel Farrelly. Crabtree was actually raised in St. John's by several aunts who, it turns out, have an interesting occupation. The solution to murder lies with finding an old pirate treasure map.

Detective Murdoch, Inspector Brackenreid, Dr. Ogden and several others are transporting serial killer James Gillies to the prison in Kingston, Ontario where he is scheduled to be executed the next day. It creates a bit of a stir among the passengers when they learn who is being transported. Among them are Aaron Rauls, a late arrival on the train and Nathaniel Henry. Both come under suspicion when the police find a dead man, Dennis Bolton who was released from the Don jail just a week ago. There's no direct connection between Bolton and Gillies but both were in the same jail at the same time. As tensions rise, it becomes evident that Gillies has arranged for several ex-convicts to be on the train - all part of his plan to escape.

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.

Detective Murdoch investigates a series of robberies where the thieves have dug through the the ground and into various shops or banks. The thieves only steal diamonds however. Murdoch suspects the thief is using some type of boring device and that he and Julia may have actually felt it burrowing under the ground the night of the first robbery. Constable Crabtree develops his own theories after interviewing Elva Gordon, a deep cave explorer who believes the Earth is hollow and that there might be an entire world of people living underground. Crabtree now believes "mole people" may be at work. That theory doesn't impress Murdoch who decides to use modern technology to track the boring machine.

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.

Detective Murdoch and his colleagues face an entirely new dilemma when they find a local industrialist, Richard Welch, tied down at the top of a telephone pole with a noise-activated bomb strapped to his chest. Mayor Clarkson orders all industries in the area shut down and the police do their best to keep the noise pollution to a minimum. Under pressure, the mayor eventually relents and work resumes, but not until after the bomb is detonated by a loud car horn. The next victim turns out to be the mayor himself and Murdoch has only 3 hours to find the culprit and deactivate the device. Meanwhile, Julia is increasingly frustrated as Murdoch has yet to ask her the big question.

Detective Murdoch investigates the death of Oliver Hoyle who is found in the billiard room of his posh club. Hoyle was part of a group of competitive puzzle solvers and he may have been killed after solving a puzzle published by Edgar Allen Poe many years ago. It appears that one of his competitors killed him to get the glory for himself. Meanwhile, Julia visits her father Lionel but arrives only to learn that her father has died. His physician, Dr. Bradley, believes he died of heart failure sometime in the night. Julia is confused, particularly when Dr. Bradley refuses to undertake an autopsy. Murdoch soon joins her and initially doubts that anything illegal has happened. He reconsiders when he learns that Julia has found a needle mark in her father's neck and a new neighbor is the beneficiary in his will.