In a cellar underneath Hindley Street, two people sit under white sheets and wait. We don’t know anything about them; they could be complete strangers, they could be lovers. They could be mannequins. In dim, menacing red light, the sheets are pulled back and Zygosity begins—in parts terrifying, in others funny, this unassuming play from Venn Street Theatre Company is an electric experience.

Named for the “genetic relationship between offspring of a single birth,” Zygosity plays with womb imagery, astrology, horror themes and the idea of escape. Held captive with no resources, the pair only have each other to rely on and when they discover their relationship to each other, things start to turn sour. All this results in some fantastic dialogue and direction from Andreas Lohmeyer and Michael Abercromby. Playing the estranged brother and sister pair, Lohmeyer and Grace Victoria are fantastic as Paul and Cassandra. Tied down and only able to move from the neck up, they give all they’ve got and manage to overcome their physical incapability with boundless energy. As a pair, they have a playful, stinging relationship, slinging barbs at one another in as loving a manner as possible. They are wholly credible as estranged twins, and give a potentially hokey concept believability.

Like the captive twins, the audience are effectively blindfolded for the whole of this performance. They are given little context, and have to make their own conclusions about the world beyond their incarceration, personified by Rose Riley as the kidnapper. She gives this role the right amount of menace and fun, to the point where you can feel yourself siding with her, and approving her burgeoning relationship with one of the captives. The sound design by Adrian Kingwell is exceptional, creating an unsettling atmosphere with sparse electric soundscapes. Ancient World’s ancient cellar is also an inspired venue choice—set dressing not required.

Is there an escape behind the door? The unanswered questions of Zygosity lead to a constantly renewing sense of interest. Kept on the edge of your seat, the show works on its unwillingness to lead the audience down a pre-determined path. Driven by energetic performances and a sharp, fresh script, Zygosity is a robust piece of theatre.