 Glasgow, 1968. Thirteen-year-old Lex Maclean lives with his mother, and his two older brothers, Alan, who plans to go to art school, and Bobby, a rather slow-witted member of the Glen gang. Lex enjoys art, but is caught up with the gangs when he mischievously fires an air gun at Malky Johnson, the gang leader of the Tongs. Charlie Sloan, the Glen gang leader, offers Lex protection if Lex will work with his gang. Malky is further annoyed with the Maclean brothers when his girlfriend Joanne is attracted to Alan.