WHAT IT’S ABOUT Famed illusionist and magician Harry Houdini (Michael Weston) is in London for a series of shows when he meets Arthur Conan Doyle (Stephen Mangan), the famed creator of Sherlock Holmes. In Monday’s opener, they forge an unlikely alliance, to help solve the murder of a nun at a convent. They are oil and water: Doyle believes in ghosts, Houdini thinks they are tricks of the burgeoning “spiritualist” movement. Scotland Yard directs Constable Adelaide Stratton (Rebecca Liddiard) to mediate between the two.

MY SAY Normally a pushover for period dramas set in 19th century London, this at long last may be my exception. Reasons why are elementary (my dear Watson): The plots are ludicrous, the casting wrong and the musical soundtrack a jarring affront.

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Let’s start with that casting issue — and maybe end with it, too. Mangan is a talented actor, and a gifted comic one, too (American audiences know him as Sean Lincoln from “Episodes”), but he’s seriously adrift here as the creator of Sherlock Holmes. Whatever lingering impressions remain of this author nearly 90 years after his death, it’s unlikely they’ll arrive at this portrayal — the congenial other half of an improbably matched buddy cop team. Meanwhile, Weston’s Houdini — as the unyielding agnostic to Doyle’s willing spiritualist — is just grating. When Doyle insists that “every religion has told us death isn’t the end, and now, thanks to science, we may be able to actually prove it,” Harry can muster only this: “What a load of crap.”

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Did Houdini and Arthur Conan Doyle know each other in real life? Indeed, they did. Both world-famous celebrities by the 1920s when they finally met, they could hardly avoid each other. But it was their shared interest in spiritualism that brought them together and (apparently) drove them apart, too. Doyle wanted to believe in the afterlife, as millions of others who had lost sons in the “Great War” did as well. Houdini wanted to expose the charlatans who were exploiting mass grief. That’s an interesting, compelling idea for a TV series. Too bad a boilerplate cop procedural had to be the series they got instead.

BOTTOM LINE A bore.