Beware of the mouse

Set in the year 1450, the tiny Duchy of Grand Fenwick, ruled by the benevolent and noble Sir Roger and armed with its army of expert longbowmen, had existed peacefully without threat of invasion for decades. But when a rascally Irish Knight stumbles across its borders with news that the French were set to attack and that they had a new weapon of mass destruction called "the cannon," the Irishman and Sir Roger must find a way to drop their differences and fight together, a feat made even more difficult when Sir Roger's daughter, the Lady Matilda becomes unduly enamored in the Irish newcomer.