about 2100
hours
`` Give me that again . '' The messenger from the Solar Guard headquarters on Mars repeated the message . `` Cadet Corbett has not been in his hotel since last night , sir , '' he said . `` He was seen leaving the service entrance at about 2100 hours . There is no report as to his whereabouts , sir . '' Standing at the foot of the ladder leading to the main air lock of the _ Polaris _ , Major Connel turned to Carter Devers angrily . `` This is the end ! ''