Jason McCubbins, Ray's business partner. The calendar is the clue to solving this murder. The police realized that since Mr. Whitcombe was wearing his watch on his right arm, he must be left handed. But the pen was found in his right hand. Realizing that the number on the calendar was written in a hurry and with his opposite hand, police matched the written number with the months of the year. So the B was an 8, thereby giving us 7-8-9-10-11: July, August, September, October, November. Use the first letter of each month and it spells J-A-S-O-N.