Johnston is a dashing attractor of spotlights who has played Hollywood gigolos and populist presidents. He has the brooding charisma to embody James Dean, should the opportunity arise. But in the world premiere of Charles Gluck's Unlikely Heroes at Mizner Park Studio Theatre, he had to meet the challenge of blending into a dysfunctional family ensemble. As the youngest character onstage — a detached video gamer symbiotically attached to his game controller — Johnston was almost too old for the role, but with acting this first rate, almost will do just fine. For much of the play, as his uncle's uncomfortable request for a transplanted organ reopens old filial wounds and cuts new ones, he escaped the explosions in the family living room by creating virtual ones on his console. By the end, however, when his character finally came to grips with the play's game-changing revelations, the eternal adolescent grew up before our eyes, processing the news with a volatility we didn't know raged within him. He added new dimensions to his character with decisions both loud and subtle so that his unlikely heroism seemed like an inevitable coming-of-age transition.