When looking for someone to adapt his novel The Curious Incident of the Dog in the Night-Time, Mark Haddon specifically sought out playwright Simon Stephens because of his “heart of flint.” That captures Stephens’s cool and clear-eyed observation of people with all their flaws, but it misses the underlying optimism in his writing that creates such an exciting tension with his flinty surfaces. His specific brand of guarded optimism was indeed exactly what was needed for Curious Incident, and is once again on surprisingly heartening display in his own play Heisenberg.

In a London train station, Georgie (Mary-Louise Parker) spots Alex (Denis Arndt), a man several decades her senior, and plants a kiss on his neck. Nothing is quite as it seems, either at that moment, or indeed as their relationship grows and changes. Out of unpredictable oscillations between self-interest and selflessness is born something that closely resembles love.

Both Georgie and Alex have massive defense mechanisms due to difficulties in their lives, yet gradually offer each other more and more company and comfort, because…well, why not? Parker can sometimes be abrasive and “too much” as Georgie – but that’s actually because she’s playing the character correctly. Similarly, Arndt can be a bit opaque, but that’s because Alex is opaque.

Stephens very successfully makes us care about two prickly, slippery people by giving us insights to the all-too-human pain that drives them. Mark Brokaw’s spare but very detailed direction serves Stephens’s script marvellously well. Recommended.

For tickets, click here.

To learn about Jonathan Warman’s directing work, see jonathanwarman.com.