When zoo worker Frank Detorri (Bill Murray) contracts the virulent virus Thrax (voice of Laurence Fishburne), inside his body--known as "The City of Frank" to its inhabitants--a white blood cell cop, Osmosis Jones (voice of Chris Rock), and a cold tablet, Drix (voice of David Hyde Pierce), join forces to fight the invading virus intent on taking over "The City." But to bust Thrax, Osmosis Jones must bypass Mayor Phlegmming (voice of William Shatner) and enlist the aid of the Mayor's assistant, Leah (voice of Brandy Norwood). When Osmosis and Thrax clash in the climactic battle of this germ warfare, Frank's life--and the lives of all the citizens of The City of Frank--hang in the balance.