Mira Barrett is an agent with the CIA.
She is an experienced field operative that is so good, her Agency handler has no qualms about dropping her into any sort of dangerous hotspot with the expectation that she would come out alive. Okay, that 'dropping' part was meant to be amusing as we meet Barrett as she lay on the ground in a Nicaraguan rainforest having just fallen, parachuteless, from a small plane two thousand feet up. She was lying there feeling her bones slowly and painfully unbreak. It took a couple of hours because there were a lot of breaks.
How does she survive as well as then heal so quickly?
Barrett is also a vampire.
We are told that two decades before we meet her, the vampires who dwell among us revealed their existance for the first time, though of course the myths and legends of such creatures have been around for centuries. Speaking of legends, we are told some are true and some are not. She can go out during the day but she works far better at night. I don't know about a stake in the heart but decapitation does end their existance, as does a really powerful bomb. Garlic - they are allergic She is faster than humans but not ridiculously so. Apparently there's no changing into a bat or wolf (that I saw) but she can hypnotize really fast and while thus 'connected' can communicate telepathically. And was we see with the air drop survival, she mends really, really quickly though she feels every part of it and it isn't fun.
Oh, there is a difference in this universe between Origins, as the vampire race call themselves, and Night Walkers, which are humans who have been turned into vampires through the legendary means. We are told there are not a whole lot of vampires out there with Night Walkers being the bigger number. It's all a bit confusing.
Barrett was already a hundred years old then as her birth year was 1893 making her 126 years old. She hardly looks much over 18, though. From what she tells us, vampires age slowly as they mature and then reach some point where their bodies says that's old enough and then they stay at that age. She did that in 2003.
She has worked for Langley for several years already. She is the Agency's only vampire. It has tried to recruit more but so far she is "the only one who's bored, reckless, idealistic or random enough to accept". Plus the pay is pretty good.
One of the main reasons why the CIA would like to have more of Barrett's race is because one of the problems that has arisen since vampires were revealed to the human world is the Dominion. That is a confederation of Origins who would very much like "to basically destroy human civilization and reduce them to being primitive creatures existing only as a food source, much the way humans keep pigs, cows, chickens, and so on". They are not nice and since they are vampires with the powers that race has, having people like Barrett is required. Seeing as she is the only one so far, though, she is kept pretty busy.