This is book number 5 in the Bright Empires series.
What do you do when you're faced with The End of Everything?
The evidence is compelling--not only is The End of Everything approaching, it's approaching rapidly. Desperation sends the Questors to the four corners of the universe in search of answers.
Tony and Gianni are in Rome gathering additional data on the collapse of the universe, and Haven and Giles are captured by Huns and taken to Byzantium.
Mina travels to Egypt to recruit Dr. Thomas Young, "the last man in the world who knows everything." But when he accompanies Mina, Kit, and Cass to the ley guarded by the giant tree, he manages to activate the ley and he and Mina disappear.
Before disappearing, Dr. Young dubbed the giant yew the Fatal Tree--but what fate is it leading these Questors toward?