Spade is a special agent for the President.
When we first meet this operative, he has already been around for quite a while with the Secret Service, earning a reputation for himself. "Smasher of a hundred counterfeiters ..." "Preserver of the live of more than one President ..." "The symbol of his vengeance, the Ace of Spades, strikes terror to the hearts of wrong doers."
That last part is interesting for he carries with him a single playing card to leave behind when he has taken out the bad guy, a marker to let people know it was he that brought down the heavy.
Apparently he needs this identifier for he is "known only as 'Spade'" while "the true identity of this agent of a hundred faces and a thousand tricks is a mystery ...." Exactly why his identity is a mystery remains, well, a mystery.
As we meet him, he is asked by the President, unidentified but certainly FDR, to work undercover for him to
handle the myriad problems the Chief Executive encounters. This means having to give up his previous job with the Secret Service but he cannot refuse his President so he agrees.
The few missions we learn about are varied but mostly have to do with the upcoming war. In doing them he encounters an enemy operative every bit as talented as he and quite lucky as well. She may lose a time or two but she always has an escape route so she survives to fight another day. Taking a cue from Spade, she likes to leave the Queen of Hearts as her calling card. Rather interesting choice considering how cold-blooded she shows herself to be.
Spade is illustrated as being a fairly tall, broad-shouldered man with "heavy brows" and a "big nose" (as mentioned by a woman) but is ruggedly handsome enough to be noticed by her.
Intrepid is a word that might be used to describe him. Or foolhardy. As he puts it on one mission, 'walking into traps gets results!' Brave and/or dumb.