Heart To Heart Theatre’s How We Think We Think begins inauspiciously. Peter Dewhurst as Tom ushers the audience to their seats, then haltingly embarks on a prepared presentation on human consciousness. Gradually, however, it becomes clear that his nervous, apologetic fumbling is all part of the act. Because this isn’t a presentation at all, it’s a play. A gripping, gut-twisting and utterly unique one-man play by Melanie Ball about a man trying to come to terms with a horrific experience. About a man trying to understand himself.

Tom was taking a southbound Northern Line service home early one morning, when a friendly American stranger struck up conversation. The pair shook hands, introduced themselves, and alighted at Stockwell where, suddenly and without warning, the stranger hurled himself in front of an onrushing train. Stunned and scared, Tom ran, clutching the last thing the stranger had ever touched: a copy of the Metro containing a single, cryptic clue.

Tom’s frantic ensuing search to uncover the stranger’s identity forms the bulk of his amateurish presentation. With the help of an overhead projector, a collection of precisely labelled newspaper cuttings, and a tape recorder, Dewhurst – as Tom – pieces together a compelling tale of obsession, depression and tragedy. Sprinkled in are illuminating snippets of pop psychology, adroitly supported by unexpectedly intriguing real-life evidence.

Throughout, members of the audience are called upon to voice an opinion, to read printed extracts out loud, or to act out short scenes with Dewhurst. For the most part, this is little more than a refreshing, creative way of elucidating or advancing the story, but at times it is utilised to devastating emotional effect: a woman sitting in the front row reads out a harrowingly sad note from the jumper’s desperately searching mother, a man next to her is asked to act out the jumper’s last living moments. It’s hauntingly arresting stuff, for which director Joe Ball deserves credit.

Dewhurst is superb. Initially earnest and honest, his Tom grows increasingly frantic and neurotic, until his reliability as a narrator is plunged into thrilling, riveting jeopardy. Suspicion and confusion hang heavily in the air, as his search for answers turns darker and darker. Is he imagining things? Was he even on that platform? Did he actually push the stranger onto the tracks? In a powerful, polished performance, Dewhurst manages to juggle these possibilities while simultanesouly maintaining a congenial, unobtrusive presence.

This is remarkable theatre: intense, shocking, and thoroughly absorbing. At its heart is a profound, universally applicable comment on our need to connect with others, an illuminating conversation about our morbid attraction to tragic events, and an inspiring plea for greater compassion from us all.

How We Think We Think is playing the King’s Head Theatre until 13 August 2016. For more information and tickets, see the King’s Head Theatre website.