The film opens in the streets of Manhattan in the late summer of 1957. There is a mounting tension set to music ("Prologue") between a white American gang, the Jets, led by Riff Lorton (Russ Tamblyn), and a rival gang of Puerto Rican immigrants, the Sharks, led by Bernardo Nunez (George Chakiris). The Jets harass the Sharks and vice versa, culminating in a free-for-all throughout the streets. Eventually, the Sharks catch the youngest member of the Jets, Baby John (Eliot Feld) on the playground. As they begin to "bloody" him, all the other Jets and Sharks rush in and start brawling. Soon, Lieutenant Schrank (Simon Oakland) and Officer Krupke (William Bramley) arrive and break up the melee. Schrank orders the Sharks off the playground and the Jets "to make nice with them Puerto Ricans" or there'll be a price to pay. Once Schrank and Krupke are gone, the Jets discuss challenging the Sharks to an all out rumble that will decide who gets control of the streets. They decide to deliver the challenge to the Sharks at a dance later that night, because it is neutral territory. Riff also explains to the Jets that they have seen other gangs (the Emeralds and the Hawks) come and go, but the Jet members state that the Sharks are different compared to the other gangs. However Riff eases the statement, that no matter the odds or the situation the Jets will always pull through.