This computer-animated film is set in World War II in London, where carrier pigeons were crucial in exchanging essential information to troops. Valient (voiced by Ewan McGregor), the name of a small pigeon, has dreams of being one of those carrier pigeons. Though he does not meet the high standards of the Royal Air Force Homing Pigeon Service, their forces have depleted due to captures and casualties and they are forced to take every able-bodied pigeon they can get.

With Squadrons A through E unavailable, Valiant is relunctantly placed in training in Squadron F. There, he befriends Bugsy (voiced by Ricky Gervais), a messy, dishonest and cowardly pigeon. Soon, Valiant finds himself delivering important messages, evading carnivorous German falcons, solving problems that are only possible for smaller pigeons, rescuing captured colleagues, fighting for freedom and the ability to make it home to a beautiful nurse pigeon.