The Summer Tree is the first book of the trilogy by Guy Gavriel Kay The Fionavar Tapestry.

The books opens in University Toronto, Canada, when professor Marcus reveals to five students, that he comes from Fionavar, the primal world, and his real identity is Loren Silvercloak. He invites them to participate to the celebration of the 50-year reign of King Ailel of Brennin.

The students (Kevin Laine, Paul Schafer, Dave Martyniuk, Kimberly Ford, and Jennifer Lowell) agree to travel to Fionavar. However David is lost during the process of the teleportation spell, but the four arrive normally in Brennin.

The first part of the tale goes around the four: Kevin and Paul are befriended by Darmaid, Ailel's son and they go with Darmaid on his visit to Cathal to meet his love interest, Princess Sara .

In Brennin, Kim is befriended by Ysanne the seer, while Jennifer is approached by Jyel, the priestess of Dana. Eventually, Kim takes the place of Ysanne and Jen is abducted by swartalfar. Paul returns there earlier than Darmaid and Dave in order to take the place of Ailel on the Summer Tree, so as to bring rain to the land. At the end, the Rangat mountain explodes, and the kingdom is ready to go to war.

The second part follows David: We go back in time to see him arriving in the plains of the Dalrei, where he got to know their customs before being ready to go to Brennin and join his friends.