Rob Stone is an agent with the Secret Service.
He is not a spy per se. He would look at you with that look if you suggested it. He was an investigator and a very good one, one that has earned the respect of the Chief Executive but his specialty was in law enforcement and he liked it that way. The reason he is in this collection of series about spies is he seems to go up against them a fair amount and he makes them not like him because he tends to get the better result in the conflict.
Stone enjoys the job he has of helping to protect the President and since the one he is currently guarding is one he likes, the job is especially satisfying. Since he has the attention of the man, though, it means he is the go-to guy when the President needs someone he trusts and can count on to do things that go a bit outside the normal protection circle.
Standing around 6' tall in pretty fair condition, Stone is not so much physically intimidating as he is with his demeanor. Knowing he was good in a scuffle and willing to take the pain to earn a win, Stone will not usually go looking for trouble but he will not back from it. He is described as "clean cut and smart looking but in an ex-military kind of way". He is said to have a humorous glint in his eyes most times but that can go away very quickly when he is confronted.
When he is not at work, which seems to take up most of his time, Stone enjoys taking part in car racing and in mountain climbing, neither activity remotely considered safe and both guaranteed to provide the kind of excitement that Stone finds rewarding.