Who pushed Charlie off the climbing frame?  A cloak-and-dagger mystery is gripping the local primary school, and erstwhile teacher's pet Elton is firmly in the frame.  He waits now outside the headteacher's office, his dreams of future eminence twisting slowly in the wind.  But he's not alone: another child is with him, a troublemaker whom the goody-two-shoes Elton would normally shun.  Will this odd couple unite in the face of a common enemy?  And more importantly... will Elton ever learn to play?

The big joke underpinning Play Time is that the characters are nine years old, yet speak in grown-up language – with a precocious vocabulary to boot.  That incongruity proves a rich vein of humour, lending extra verve to witty turns of phrase, and heightening the irony when the nine-year-old's view of the world shows through.  One gag, linking a misunderstanding of where babies come from to a naïve rationalisation of gender inequality, is a miniature masterpiece – saying more through the kids' misplaced trust in logic than many an earnest political play has achieved.

The two characters fall quickly into familiar patterns, but are none the worse for that.  Elton – whose dumpy styling borrows quite a lot from David Mitchell – is the clever, awkward, sweetly vulnerable one; his co-conspirator is more mercurial, halfway between a mentor and a nemesis.  Oliver Neck and Matt Zeqiri, who also jointly wrote the script, build rounded characters around these simple templates, and the shifting loyalties between the pair of them form the backbone of the plot.

A big part of the pleasure is the journey back into your own past: the reminder of how pencil cases seemed overwhelmingly important, the recollection of when you entered formal negotiations to become someone's friend.  Not all the memories are pleasant ones, of course, and the cruelty children mete out on one another is captured too.  But it's always cartoonish – immature, in a literal way – so while there's certainly some discomfort there, it never overpowers the comedy.

Perhaps there's a little more to be found in the darkness, especially surrounding the awful, creeping suspicion about exactly what Elton may have done.  The moment where the young boys discover the concept of death isn't as poignant as it might have been, and they could usefully give their scene-ending dramatic turns a couple more beats to sink in.

The conclusion, though, is perfectly judged – utterly logical, yet for me at least, a total surprise. There are other surprises too, unexpected tangents to the performance which I daren't even mention for fear of spoiling them.   In the end, Play Time's uncomplicated plot belies a sophisticated and well-worked comedy, performed with panache and irresistible warmth.  Go see it; you'll have fun.