Brown’s finest music, and Platt’s most heart-wrenching work, come during his trial, as three factory girls (who have been coached to lie) hauntingly harmonize their testimony like Abigail from “The Crucible.” Brown has yet to top it in any show. When Leo gives his statement, and Platt sings that his character is unemotional and awkward but innocent, it’s the tears-free opposite of when he sobbed at the end of “Dear Evan Hansen,” but the gut-punch is the same. The second act has more built-in structural issues, as Lucille works tirelessly to appeal her husband’s verdict and enlists the help of Governor Slaton (Sean Allan Krill) to get Leo home. A galvanizing number is followed by minutes of aimless procedural wading. But there are few sublime moments. As another factory worker, and suspect, Jim Conley, Alex Joseph Grayson wails the song “Feel the Rain Fall,” which is gorgeous but pops up out of nowhere. And Diamond, whose combination of fragility and power is thrilling for an actress so young, brings an electricity to her duets with Platt: “This Is Not Over Yet” and the romantic “All the Wasted Time,” which fades into the musical’s devastating conclusion.