Though long celebrated as one of our most versatile screen stars, four-time Academy Award nominee Willem Dafoe might not seem like the obvious choice to portray a swaggering, playboy billionaire modeled on Greek shipping magnate Aristotle Onassis.

Just ask Willem Dafoe.

“Me? Playing a Greek shipping tycoon?,” the actor tells Variety on a recent visit to Athens. “I don’t think so.”

Dafoe is perhaps selling himself short. But for his latest film, “The Birthday Party,” which premieres Aug. 7 in the Piazza Grande at the Locarno Film Festival , the Wisconsin-born star takes on a new challenge, stepping into the exquisite loafers of a self-made Greek billionaire planning an elaborate birthday fete for his daughter.

Adapted from the novel by U.K.-based Greek author Panos Karnezis, the

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