In A Ring of Endless Light ( 1980 , ISBN 0 - 374 - 36299 - 8 ) , Zachary reenters Vicky 's life the following summer .
Having failed to write or call during the period covered in The Young Unicorns .
In A Ring of Endless Light ( 1980 , ISBN 0 - 374 - 36299 - 8 ) , Zachary reenters Vicky 's life the following summer , although having failed to write or call during the period covered in The Young Unicorns .