Risked (The Missing, #6)

Jonah thought that after his last adventure in 1903, he and his sister Katherine would have a break from time travel for a while. For the first time, he’s willing to look into his own identity in the past, and he thinks this is his chance.

But he barely has time for a single Google search before he, Katherine, and their friend Chip are tricked and zapped back to 1918--and to the house where the Romanov family was imprisoned after the Russian Revolution. Trapped without a fully working Elucidator, the three kids still hope they can escape and save the lives of Anastasia and Alexei Romanov.

But is it possible to change time that much when modern-day scientists have identified the entire Romanov family’s remains?

Description from http://haddixbooks.com/books/risked.html.