A mouse named Gamba learns of the island of Yumemishima, where mice are being terrorized by Noroi the white weasel. Gamba gathers a group of seven mice to journey to Yumemishima and put an end to Noroi's tyranny. Based on the 1972 novel Boukenshatachi: Ganba to 15-hiki no Nakama by Atsuo Saitō.