who was missing a sock?
 "Say, who swiped one of my socks? I can't find but one, and I left 'em together." He began to toss things left and right in search of the missing article. 

Meanwhile Upton was down on his knees fumbling under his bunk. At Hal's complaint he looked up suspiciously. "I can't find one of mine," he sputtered. "Somebody's been putting up a job on us. Hi! What the----" He finished by pointing toward the fireplace. 

Hal looked. There hung his missing sock. Also one of Upton's and one of Sparrer's, all three misshapen and bulging.  