It is an intriguing and unsettling idea. Why must all unknown soldiers be dead? Why couldn't a combatant return from war physically but not mentally, and then spend the rest of his life trying to rebuild a fractured identity?

Using the book by Jean-Yves Le Naour as inspiration, vibrant young company Simple8 have concocted a drama about just such a soldier who arrives demobbed and amnesic at a French railway station in 1918.

Multiple actors play the virtually silent central character, a device that perfectly suggests a blank canvas onto which the world can project its own expectations. Endless families come forward to claim the soldier - the repetitiveness of which can't help becoming cumbersome to Sebastian Armesto's production - whose humanity crumbles a little more each time he is gawped at and argued over.

Still, assured turns from the eight-strong ensemble, including Tom Mison as an amusingly insouciant journalist, keep us focused on this quiet casualty.

• Unknown Soldier, until 15 March (020 7503 1646, www.arcolatheatre.com).