Regulus, the brightest star of the Leo constellation, takes it into his own hands to go after a star, Dubhe, who ran from his constellation and fled to Earth. In attempts to defeat him or make him return, Regulus encounters a messager in medieval times named Pip who gets him caught up in his kingdom's war. Mistaken for a knight, Regulus must help the kingdom defeat the enemy, all while struggling to fit in and do his part as a celestial object from the sky.