With a bushy gray beard

Health issues forced Robin Williams to cancel a planned 2009 Broadway engagement of his standup tour, Weapons of Self Destruction. So it seems oddly fitting he should arrive instead in a fascinating role that combines profane comedy, war and existentialism. Think of him as Lenny Bruce meets Friedrich Nietzsche in the body of a man-eating predator.

With a bushy gray beard, ragged clothing and no hint of a tail or stripes, Williams plays the surly old beast in the title of Rajiv Joseph’s bracingly original Pulitzer-shortlisted play, Bengal Tiger at the Baghdad Zoo. He spends most of his stage time, however, not prowling the cramped confines of a mangled cage in the bombed out zoo, but wandering the burning city as a ghost, tormented by soul-searing doubts.

Contemplating his damnation over the basic primordial impulse to kill and eat, the atheistic Tiger asks, “What if my very nature is in direct conflict with the moral code of the universe?” His quest for atonement is just one of the mordantly funny philosophical threads of this imaginative work.

Set in the early days of the American occupation, the play was inspired by a news item about the Baghdad Zoo. It’s a black comedy, a grisly horror show and a metaphysical ghost story.

Two U.S. Marines guard the Tiger’s cage. Tom (Glenn Davis) gets a little too close while taunting the animal, and loses a hand. This prompts his dim buddy Kev (Brad Fleischer) to shoot the Tiger with a gold-plated pistol looted from the Hussein Brothers mansion. As opening scenes go, it’s an attention-grabber.

Cut to Kev attempting, or not, to explain the colloquial usage of "bitch" in a knock-knock joke to Musa (Arian Moayed), a former gardener at the Hussein Palace, now working as a U.S. military interpreter. During a tense night raid, Kev’s fragile equilibrium crumbles, landing him in hospital on suicide watch. A visit from Tom, returning from the U.S. with a prosthetic hand, does little to calm him. The presence of the Tiger’s ghost does even less.

Much of the play takes place in a garden full of tattered topiary animals sculpted by Musa at the behest of Uday Hussein (Hrach Titizian). “This place is lousy with ghosts,” observes the Tiger. Designed by Derek McLane against a backdrop of dusty Middle Eastern splendor and exquisitely lit in sepulchral gloom by David Lander, the garden makes an arresting, other-worldly home for those unquiet spirits. In this decayed playground, the dead gain unexpected knowledge, even if true enlightenment often eludes them.

The urge to destroy is passed from character to character and from the dead to the living. The most unsettling transactions are those between the teasing, sadistic Uday and Musa, whose sister (Sheila Vand) died at the hands of the despotic scion.

Moises Kaufman (The Laramie Project, 33 Variations) directs this beguiling play with quicksilver shifts in tone to match the volatile, questioning nature of Joseph’s writing. Scenes of macabre, circus-like atmosphere segue to dream-like fugue states; biting humor is interspersed with poetic musings; symbolic imagery abounds; shocking violence gives way to wrenching despair.

Those altered states are also channeled by the gifted cast. Fleischer and Davis, whose characters are first depicted as gung-ho grunts, grow steadily more affecting in different ways. Titizian and Moayed are standouts, the former as an egomaniac with a malevolent sense of irony, his basest instincts fed by war, and the latter as an artist whose purity of heart is perverted by cruel experience.

Williams has not given a performance this subdued in years. He commits to being part of an ensemble, never ramping up into a star turn. There’s no comic shtick in his thoughtful Tiger, yet in the animal’s eye-rolling disdain for the idiotic lions that fled the zoo early, his playful needling of Kev or his antagonistic dialogue with a God he doesn’t believe in, the ripples of humor are rich and flavorful.