More than 350 artists have starred in Tim Crouch’s An Oak Tree—a play with only two roles. Since its premiere, in 2005, every performance has stayed true to Crouch’s original vision: one actor steps onstage with no prior knowledge of the script or story. The premise never changes. A father and daughter are in a car accident, and the driver who caused it is a hypnotist. The daughter dies. Later, the father volunteers for the hypnotist’s stage act—and that’s where the audience meets them both. In this production, directed by Crouch, Karl James, and Andy Smith, Crouch reprises his role as the hypnotist. Each night, a new guest actor—drawn from a lineup that includes David Tennant and Indira Varma—is revealed to the audience in real time. All that actor has been told is that they’re playing a grieving parent. —Jeanne Malle