Is it a bird? Is it a plane? We’re just not sure, says Katie Jarvis, who fails to determine whether she’s watching a detective drama or a comedy farce. But who cares? It’s fun, anyway.

So I’m going to compare The Perfect Murder to superman. But not in a Bernard Shaw way. Not exactly in a Christopher Reeve way, either, to be honest. More in an:

‘Is it a bird? Is it a plane?’

sort of way.

Because I sat through it – thoroughly entertained, for the most part – thinking:

‘Is it a farce? Is it a comedy? Is it a detective drama? Is it a psychological thriller?’

Honestly; who knows?

The lady in the seat next to me is a big Peter James fan. Before the curtain rises, she tells me about one of his detective novels, in which men at a stag party do bury the groom alive in a coffin (as you do). They intend to scare him – to go back and dig him up; but they’re killed in a car crash before they can return. (I hope I’m not giving anything away here; I wouldn’t know – haven’t read any of them myself.)

“They’re creepy, his novels. Atmospheric,” she says.

The Perfect Murder, adapted for stage by Shaun McKenna, was inspired by a charity dinner that Peter James once attended. He found himself next to the then-chief constable of Sussex, Martin Richards. As the Everyman programme (always such an interesting read) details, James asked him if there was such a thing as the perfect murder. “Absolutely,” he replied. “It’s the one we never hear about.”

For James, this was a light-bulb moment.

Of course! he thought. The murder that isn’t a murder!

Tonight, the theatre is packed. A minority of the audience is probably here because they’ve read these best-selling novels, starring detective Roy Grace. The rest is here – I guess - because they’re EastEnders fans. (Of which I’ve never watched an episode, but I believe they tend to bury people under patios. Significant.) And this production stars two of the EastEnders cast: Shane Richie as Victor Smiley, and Jessie Wallace as his wife, Joan. (Interestingly, when I google the two, I get the headline that they blasted EastEnders bosses over ‘farcical storylines’, which begs a question… But hey ho.)

The first half of The Perfect Murder is a long scene-setter. Victor – I really like Shane Richie’s performance – tells his prostitute lover that his wife ‘doesn’t understand me. I’m going to kill her’; not least for the £400,000 insurance policy he took out on her a fair old while ago. (He’s pretty good at long-term planning.)

Then we switch to his home-life, which consists of a lot of bickering with Joan, some of which is reasonably amusing. “Benedict Cucumber Patch? I like him. Nice little bum.” It soon becomes clear that, despite Joan’s titillating attempts with crotchless panties and a peekaboo bra, the magic in this marriage has died. And, what’s more, Victor and Joan each separately intend for one further death, to boot.

Thus the comedy/farce – amply amplified by Stephen Fletcher as Joan’s lover, Don Kirk. Strangely interwoven are the scenes where detective Roy Grace (Benjamin Wilkin) pals up with clairvoyant prostitute Kamila Walcak (entertainingly played by Simona Armstrong), which seem straight from the heart of a psychological thriller.

And the second half morphs, at times, into a horror story, too.

It is funny. There’s at least one bit where the entire audience jumps in startled unison. And there are twists. I can see why it shouldn’t work. I can see the flaws, the disparate qualities, the parts where what I think is a plane turns out to be a parrot. But I didn’t not enjoy it. I didn’t not enjoy it one bit.

The lady in the seat next to me loved it. And she’s never seen EastEnders either.

• The Everyman Theatre is at Regent Street, Cheltenham, Gloucestershire GL50 1HQ, box office 01242 572573; www.everymantheatre.org.uk