"A secret has an answer," says a character in J.T. Rogers's drama, adding that a mystery remains a mystery. The analogy's false, since mysteries have solutions, but it works for Madagascar, which moves forward and backward, raveling and unraveling at the same time. A man has vanished. For much of Act One you don't know who, only that a good percentage of people who choose to disappear are successful. In Act Two, the mystery becomes: why did he leave? Like a poison, the solution(s) to the mystery infect those left behind. The play's set in a stripped-down hotel room, in Rome, above the Piazza di Spagna. It takes place today, as Nathan confesses; and three days ago, as young June dares to remember; and five years ago, as June's mother Lillian builds a wall of denial and stands perplexed behind it. Like Chinatown, the play's title becomes a geographical locale and the site of metaphorical jazzercise. The North Coast Rep's offering a capably done staging, for the most part. Marty Burnett's creamy yellow-gold hotel room walls peel like a sunburn, and M. Scott Grabau's lighting expertly frames faces. Though they could put more variety in their deliveries, the cast performs admirably: Rosina Reynolds (in a curly blond wig), stately and fracturing as Lillian; Frank Corrado, humble, quizzical Nathan; Christy Yael's June, an ocean of subtexts. In some ways, how the playwright weaves clues and red herrings (and admonishes his audience to heed every one: "You're not paying attention!") becomes as, if not more, interesting than the characters' upended expectations, since he forces you to listen to every word rather than respond emotionally to the situations. This has a rational, distancing effect. For people who require "structures" and "grids" (the playwright's words) of order, Madagascar may frustrate. But the play has some terrific writing, and the conundrum is such that, were an easy solution given, it would frustrate even more.