The Summer of Friendship was a summer named possibly after the friendship of Badgermum Cregga and Mhera the otter. During this summer's Nameday, a great feast was held at Redwall Abbey. That same summer, Rillflag was murdered by Juskarath at the ford near Redwall and Deyna was captured by them. Their mysterious disappearance caused much grief for Mhera, who was Deyna's sister and Rillflag's daughter, and Filorn, who was Deyna's mother and Rillflag's wife. Also during this summer, a visiting hare, Boorab the Fool, taught Kitchen helper Broggle to get rid of his stammering.
The Summer of Friendship occurs in Taggerung.