Beyond the Grave

Amy and Dan are hot on the trail of the fourth Clue, but their ruthless
relatives will stop at nothing to eliminate them from the
competition. Their hunt leads them to an ancient city that has been
a hot bed of Cahill activity for centuries. All that stands between
the siblings and the Clue is a cryptic riddle, a missing relic,
and the secret of their grandmother's past. The clock is ticking
for Amy and Dan, but can they really solve a mystery that has
eluded their ancestors for generations?