Checkmate was not your ordinary detective show. Well, actually, it was, but what was so different was that Revue packaged it in conjunction with Jack Benny's production company. Now, before you scoff, bear in mind that Benny did do some drama during his career, guest-starring with Dick Powell on Four Star Playhouse, for example.
Checkmate lasted just 2 seasons, probably because of a glut of crime dramas on television at the time. You had a trio of sleuths (Sebastian Cabot, Doug McClure, Anthony George) solving crimes in normal fashion. George left The Untouchables for this gig.
Future Oscar winner John Williams composed the score, and would be responsible for quite a few more themes for both Revue/Universal and 20th Century Fox during the 60's before turning full-time to movies.
Following is the episode, "Waiting For Jocko", with guest star Jeffrey Hunter. The score for this episode was composed by Pete Rugolo:
Of course, Doug McClure moved directly to another Revue/Universal entry, The Virginian, after Checkmate ended, and that would keep him busy for 9 seasons. Sebastian Cabot is better known for the original Family Affair than anything he did before or after.