midnight
It said very little . Described a tiny fragment of gold quartz rock the size of a walnut which would be found under the giant microscope in the laboratory ; and told Alan to give it to the American Scientific Society to be guarded and watched very carefully . This note was found , but Dr. Kent had vanished ! There had been a midnight marauder . The laboratory was on the lower floor of the house . Through one of its open windows , so the police said , an intruder had entered . There was evidence of a struggle , but it must have been short , because neither Babs , Alan , the housekeeper , nor any of the neighbors had heard anything .