How was the conflict solved in Found by Margaret Peterson Haddix?

The solution is "JB" (Janitor Boy) tells Chip and another boy named Alex that there real family is in the past (15th century) where they could die and he tries to take them there. Jonah and Katherine don't belong in the 15th century but come along anyways. JB tries to talk them out of going but they insist and finally JB agrees to let them try to fix time without letting Chip and Alex die. What happens in the 15th century while trying to save Chip and ALex is in her next book, Sent.