The 48th Hour

The priceless necklace once belonging to the Lady of Tikal has been stolen! It was due to arrive at the museum late last night, with only the curator and security guard on duty. Both have been taken into custody and held for 48 hours of questioning. Both are claiming the other is responsible. The curator claims the guard forged her signature on the purchase order and secreted the necklace away in her office. The guard claims the curator stole the necklace, even though she claims to have never seen it. A copy of the purchase order has been produced with the curator's signature. Is it a forgery? Who is lying? Will you find the necklace in time?