Growing up in a housing estate in Glasgow, Mungo and James are born under different stars --- Mungo a Protestant and James a Catholic --- and they should be sworn enemies. Yet against all odds, they fall in love as they find sanctuary and dream of escape in the pigeon dovecote that James has built for his prize racing birds. But when Mungo’s mother sends him on a fishing trip to a remote loch with two strange men, he will need all his strength and courage to find his way back to a place where he and James might still have a future.

Hugh “Shuggie” Bain's mother, Agnes, walks a wayward path: she is Shuggie’s guiding light but a burden for him and his siblings. Married to a philandering taxi-driver husband, she keeps her pride by looking good. But under the surface, she finds increasing solace in drink and drains away the lion’s share of each week’s benefits on cans of extra-strong lager hidden in handbags and poured into tea mugs. Agnes’ older children find their own ways to get a safe distance from their mother. Meanwhile, Shuggie is struggling to somehow become the normal boy he desperately longs to be, but everyone has realized that he is “no right,” a boy with a secret that all but him can see. Agnes is supportive of her son, but her addiction has the power to eclipse everyone close to her --- even her beloved Shuggie.