A supernova explodes on Broadway every night this spring at the Belasco Theatre in End of the Rainbow, directed by Terry Johnson. For two hours, the British actress Tracie Bennett laughs, rants, wheedles, flirts, swears, and sings her heart out with a bursting energy that stuns her audience. Who is Tracie supposed to be? Why, the troubled diva Judy Garland, of course, at the burning tail-end of her career, performing her final shows in London in 1968 at a club called Talk of the Town on the eve of her fifth marriage (to a handsome young musician and entrepreneur named Mickey Deans). Backed by a live band, she sings “Just in Time” and “Come Rain Or Come Shine,” her eyes glinting with ravishment, clearly thinking of her young fiancé (played by Tom Pelphrey, who admirably conveys Mickey’s exasperated devotion). Judy’s fans know that Mickey entered Garland’s life far too late to save her from the diet of pills and alcohol she relied on to buoy her spirits. “Whenever I drink water, I always feel I’m missing out on something,” she says teasingly, refusing to be saved from herself.

But in a way, for viewers of this new play by Peter Quilter, which opened last night, it almost doesn’t matter which diva Bennett is playing. Her larger-than-life performance—coming more than 40 years after Garland’s death (in London in 1969, at the age of 47, of an accidental overdose of Seconal)—feels curiously timeless: It can stand on its own. Her voice truly does resemble Garland’s in its power and emotion. The weekend before opening night, a dazzled young husband and wife walked out after the show, shaking their heads. “She [meaning Ms. Bennett] is 50?” marveled the husband. “She must have taken some of those pills, too,” joked his wife. But Bennett’s natural talent is nothing to laugh at. She created this role for the London stage and now brings Garland back to her home turf, alive and more vital than ever.