Footprints at the Window — Phyllis Reynolds Naylor

In this conclusion to the York Trilogy, is Dan closer to answering his questions, and discovering who left the footprints at the window?
Dan has had enough of the uncertainty surrounding his life these days. While he may not be able to change his family's troubling secret, he intends to put a stop to his encounters with mysterious gypsies -- both in the present and the past.
By summoning the gypsies to join him, Dan is once again propelled into the past, this time to the era of the Black Death. Will Dan survive the widespread disaster that threatens to destroy the world as he knows it? And if so, will it change him forever?
Dan's journey begins with Shadows on the Wall and continues with Faces in the Water.