In The Spanish Prisoner, David Mamet's entertaining shell game, all the elaborate, high-stakes maneuvering revolves around what Alfred Hitchcock called a McGuffin, a device used to forward the plot that can otherwise be ignored. Here, this vaguely described but coveted item is called The Process, a formula devised by Campbell Scott that will "control the global market," bring competitors to their knees, and allow his boss (Ben Gazarra) an early beachside retirement. Honest, courteous, and good-naturedin Mamet's world, a classic dupeScott tries to protect his invention from any number of possible scam artists, including an extravagant millionaire (Steve Martin), his ingratiating secretary (Rebecca Pidgeon, Mamet's wife), and the company lawyer (Ricky Jay). The Spanish Prisoner, Mamet's fifth film as a director, marks a welcome return to the sleight-of-hand trickery of his first, House Of Gamesand in many ways, it's an improvement. For one, his current wife is a better actress than his former wife, Lindsay Crouse. But more importantly, while his writing remains as crisp and economical as ever, Mamet's once-creaky minimalism has finally become a cinematic asset. The mesmerizing air of paranoia, helped along by another stately score by ace composer Carter Burwell (Fargo), is the result of Mamet's newfound precision in revealing certain details while hiding others. In his best role since the two he wrote for himself (Roxanne, L.A. Story), Martin's charisma wrings just the right amount of charm out of Mamet's terse dialogue, and Scott, an underrated actor, makes an ideal everyman. With The Spanish Prisoner, Mamet confirms that he is not only one of America's most vital playwrights, but one of its best magicians, too.