The Wings of Victory by Fred M. White

Markham jumped to his feet, the first of them there to understand that there was something serious. He knew, in the ordinary course of things, that Bevill's absence would have meant little or nothing. For instance, it would have been nothing strange for that eccentric old gentleman to go off in his absent-minded way to the bungalow and there remain for a day or two without advising his friends of his whereabouts.

But this Markham felt by instinct was a different matter altogether.