In 1933, the German X-ray technician Carl Tanzler (who often went by Count Carl von Cosel) snatched the body of a Cuban-American woman, Elena Hoyos, from her Florida mausoleum, to preserve her as his bride. Carl, you see, had been convinced that his patient Elena, suffering from tuberculosis, must be his soulmate, and he insisted that mere death could not part them. These bizarre real events form the basically true-to-life plot of It Happened in Key West, the unlikely new musical premiering at the Charing Cross Theatre this month. Does such a tale make for a horror story? A Monty Pythonesque comedy? A tragic romance? Good possibilities all, but this production, smoothly staged but constantly careening between grimly saccharine and goofily satirical, would suggest the creative team hasn’t quite made up its mind yet.

It Happened in Key West is at its best when at its comedic broadest: a production number late in the second act in which the townspeople list off the hints they should have picked up on that Carl’s new girlfriend is, in fact, a corpse, feels wittily refreshing and culminates in – what else? – a kick-line. It’s not revelatory, but it’s enjoyably silly and cuttingly spontaneous in the style of The Book of Mormon and Spamalot. (If you’re in the market for a wholly charming corpse-centric musical, might I also recommend exhuming Ahrens and Stephen Flaherty’s Lucky Stiff, a whimsical piece about an English shoe salesman tasked with wheeling his deceased uncle on one last jaunt to Monte Carlo?)

More often, though, It Happened in Key West takes itself far too seriously, and the first act’s laborious trek to Elena’s demise (already referenced in the prologue) rarely offers any strong sense of tension or irony – the effort expended towards getting the audience to invest in this icky relationship feels like misplaced energy. The show ultimately attempts to demonstrate that Carl’s upkeep of Elena’s rotting remains is just a post-mortem manifestation of a timeless romance, but Elena quite unambiguously declares herself uninterested in Carl romantically before she dies. The celebration of Carl’s commitment to pursuing an unreciprocated crush when the girl’s too dead to speak for herself leaves a sour taste.

Wade McCollum’s single-minded Carl becomes gradually more palatable as the show goes on, like a creepy acquaintance you avoid if you can help it but whose idiosyncrasies no longer frighten you each time you make small talk. Even if he sounds and looks remarkably like Neil Patrick Harris’ Count Olaf from Netflix’s A Series of Unfortunate Events, McCollum makes this role (in which he exclusively sings and speaks about his love for Elena) feel a little bit more fleshed out, so to speak, than it really is, especially as Carl lovingly touches up the corpse. At the same time, composer Jill Santoriello (of Broadway’s A Tale of Two Cities) keeps pushing McCollum into his falsetto range as he courts Elena, which does more to enhance the sense that Carl is unhinged than to humanise him.

There’s clear craft surrounding the production, though: Marc Robin’s staging and choreography are slick throughout, and Louise Rhoades-Brown’s soaring video design quickly becomes a gorgeous highlight, especially in an imagined flying sequence. As Elena, Alyssa Martyn gets to show off a shimmery, delicate soprano – it’s just a shame that Carl’s infatuation seems to be entirely about Elena’s appearance and there’s no authorial intention of stretching the role towards the three-dimensional. Santoriello’s music never quite captures the dramatic heights of Carl’s disturbing passion, but she still traces some nice, simple melodies (like Elena’s sweet “What More Could I Wish For?”) and channels atmospheric quasi-Cuban rhythms. The lyrics, by Santoriello and Jason Huza, often strain too far for attention (“skull dent” and “annulment” stands out as a particularly distracting off-rhyme). Moments of the book, with credit shared among the aforementioned collaborators and Jeremiah James, most succeed when there’s a quirky self-awareness present that’s often lacking elsewhere.

In the biggest misstep of all, It Happened In Key West’s creators seem to share Carl’s monomania: where he sees nothing but Elena, they see nothing but Carl, and the deep dive into his fanatical psychology begins to feel obsessive rather than expansive. Despite the large cast, all other characters receive only cursory attention, mainly because only Carl and Elena are given any substantial singing to do. The musical silencing of the supporting roles reads as an invitation to ignore them, and, although Johan Munir makes a nice impression as the sympathetic Mario, Elena’s brother-in-law, it’s unclear how he (or anyone else in Key West) might have been changed by witnessing Carl’s warped love. While Carl might ultimately win the audience’s pity, he’s still depicted as too nuts to turn that pity into understanding; there’s no one left, then, whose transformation can make this story matter much. As it happens, the real Carl Tanzler had a neglected wife, Doris, with whom he had two daughters – now there’s a side of the story I’d like to see resurrected.

It Happened in Key West is playing at the Charing Cross Theatre until 18 August

Photo: Darren Bell