[Danger Boy #4] City of Ruins by Mark London Williams

Danger Boy is back! With the deadly slow pox spreading, the time-traveling trio hurtle back to Jerusalem circa 583 BCE.

After another close call, the good news is that Eli Sands, aka Danger Boy, is back in San Francisco in 2020. The bad news is that Eli and his friends, Clyne the evolved dinosaur and Thea the Alexandrian scholar, are being held captive by the government agency DARPA. Since their last foray into the Fifth Dimension, it seems history has been unraveling everywhere, and the deadly slow pox virus is spreading fast. DARPA's plan is for Eli to visit ancient Jerusalem. But Eli and crew discover that the city is in ruins from a Babylonian invasion, and soon an angry mob is ready to stone them. Will Danger Boy and his friends find their way home again?