Downton meets Dexter in A Gentleman’s Guide to Love and Murder

What is it with Broadway and its obsession with serial killers? From 1979's Sweeney Todd to this year's American Psycho, there is a long tradition of having mass murderers sing as they slaughter, furthering artistic aims serious or satirical. Or simply silly as in the case of A Gentleman's Guide to Love & Murder, the oddball operetta that won the Tony Award for best musical in 2014.

If you've ever wished for a crossover episode between Dexter and Downton Abbey, or longed for a musical that mixed Gilbert and Sullivan with the Grand Guignol, this is the whimsical show for you.

In the dying days of Edwardian England, a man of limited means named Monty Navarro (Kevin Massey) learns from a mysterious visitor that his recently deceased mother was actually a member of the wealthy D'Ysquith family. Not only that, he is ninth in line to become the Earl of Highhurst.

This news doesn't immediately turn Monty murderous, but a subsequent rejection from his social-climbing girlfriend Miss Sibella Hallward (the wonderful Kristen Beth Williams) and a legal threat from the first D'Ysquith he contacts certainly make him furious. And so when the chance comes for Monty to save the life of Reverend Lord Ezekial D'Ysquith (eighth in line to the earldom), drunkenly teetering at the top of the bell tower of the ancestral family church, the young man decides not to take it.

One death by non-intervention turns into a plot to murder his way to the top – one D'Ysquith at a time.

The theatrical twist of the show is this: All the D'Ysquiths that stand in Monty's way are played by the same actor. In the tour now in Toronto, John Rapson finds many enjoyable ways to skewer upper-class British stereotypes from a closeted country squire to an imperialist lady philanthropist to a vegetarian, eugenist bodybuilder.

"Why are all the D'Ysquiths dying? It seems that all of London's shaken to the core," sing the small ensemble at the top of the second act. "To lose one relative, one can certainly forgive, but how can you excuse losing two or three or four – or seven." (There are winks to Wilde and other period dramatists in the scenes and lyrics by Robert L. Freedman.)

While Rapson's performance is the showier one, I was more impressed by Massey playing it pokerfaced. He has a did-I-do-that? look out to the audience that never ceases to amuse.

And while the murder got giggles and gasps on opening night, the love aspect of the play is more subversive. Monty ends up in a love triangle between Sibella and a D'Ysquith woman named Phoebe (the delightful coloratura soprano Adrienne Eller) that confounds expectations. The three have a show-stopping tune called I've Decided to Marry You in the second act that is as enjoyable – both musically and comedically – as any of G&S's great trios.

Early scenes can be a bit of a slog as the show seems to be mimicking Edwardian exposition-heavy drawing room dramas as much as mocking them. But director Darko Tresnjak's droll staging and especially Steven Lutvak's pretty, witty score, eventually got me on its side – and the show finally won me over with the sheer amorality of its ending.

A Gentleman's Guide to Love and Murder (mirvish.com) continues to June 26.