The Battle of the Mods.

In Liverpool there's a gang war between the Mods (who dress in the latest fashions and styles) and the Rockers (who are more into the '50s "greaser" look). Ricky, the son of a wealthy businessman, is a Mod guitar player, and in a gang fight with some Rockers, his girlfriend is killed. He leaves Liverpool for the continent and winds up in Rome, where he becomes involved with his father's mistress.