Impostors. Book 2. Haddix M.P.

Is there a world that is exactly similar to ours? Until their mother disappeared, the Greystones did not know about another dimension. This place is very dangerous, and it was in his trap that his mother landed. The guys are sure: if you do not pull it out of there as soon as possible, a big trouble will happen. But how to do this when the only hint is a strange confused cipher? And even a smart Emma after three hundred and seventy -two attempts could not solve it... Will the Greystones get into the mirror world and save my mother before the irreparable thing happens? Strange deeds "!