Red Pyramid by Rick Riodan

In the book Red Pyramid by Rick Riodan, the protagonist Carter and his sister Sadie  begin to find a bit more about their father in a very dangerous life threatening, unexplainable situation. When their goes to view the Rosetta Stone (not the computer program) their dad lands up releasing some acient,evil,demons. when their father along with the demons vanish, sadie and her brother are left dumbfounded until  the FBI comes and takes Sadie and Carter to the grand parents house, and are ordered to be deported and are forced to leave in the remaining 24 hours from london. And now find themselves in the magical hands of their old forgotten uncle Ramos. And are now on a journey to retrieve their fathet from the spirits but the question remains how AND WHERE?