To be honest, I’m not quite sure what to make of the latest offering from the Watermill.

It’s enjoyable, though a bit long – there’s a lot of somewhat mysterious padding and it could do with having quite a bit more pace in the wordy bits – and I can’t decide if it’s a deliberately hammy spoof, a super-stylised homage or a murder mystery that likes a bit of singing.

There’s a lot of necessary scene-setting as the story – based on an Agatha Christie tale featuring her perky sleuths Tommy and Tuppence, and adapted by Sarah Punshon and Johann Hari – is complicated and is made more tricky for the audience by each actor playing many parts.

At one point the audience was, rather oddly, asked if anyone was following the plot, and there was a resounding, ‘No!’, which made me feel better.

Tommy (Garmon Rhys) and Tuppence (played by a perky Emerald O’Hanrahan) meet at the Candlelight Club and decide to have an adventure.

I can’t begin to explain the plot, but it involves murder, the British government (Nigel Lister), the Russians, someone called Jane Fish (Sophie Scott), an American billionaire (Keiran Buckeridge), a treaty lost when the Lusitania sank and the need for Tommy and Tuppence to solve it all within a week, or Britain will fall.

The acting is as terrific as you’d expect, with some standout moments. Philip Morgan, who I saw as the brilliant Captain Hook in Peter Pan, is peerless in every one of his many incarnations, in the end only needing to look at the audience to make everyone laugh.

Elizabeth Marsh not only plays the sultry Rita, but also the hirsute Russian Kramenin, with more success in one than the other, but that might be quite deliberate.

Clever staging almost outdoes the acting – watch out for a moment of peeping through the keyhole and the slideshow of the Lusitania sinking – and sometimes comes as something of a relief from trying to work out what’s going on.

It’s certainly different and good fun, if a bit strange. It’s not Miss Marple or Poirot, but it’ll get us all in the mood for Agatha Christie’s 125th anniversary celebrations this year.