He's no longer enamoured with all the money he's made from his gruesome best-sellers.
He's done his time signing women's breasts at book launches.
Bored with success, he foists himself upon the New York Police Department, offering his services as a left-field crime-solver, in exchange for inspiration for his next gritty thrillers.
Naturally, for a show billed as a modern take on Murder She Wrote or Moonlighting, there's plenty of writer-police detective chemistry (disguised as contempt) with his leading lady, police detective Kate Beckett (played by newcomer Stana Katic).
"Their relationship is a little like dancing," says Canadian actor Nathan Fillion, who says he talked his way into the role of Richard Castle when he was working on Desperate Housewives (he played Katherine's husband, Adam).
The pair of them attempt to get to the bottom of a series of grisly murders - a serial killer with a penchant for rose petals, a body floating in a swimming pool - although it's clear the conservative, strait-laced Beckett isn't keen on having this outlandish creative dude invade her professional space, treating each murder as nothing more than a plot device he can rip off.
It probably doesn't help either that she's a trained professional and he gets by on picking up on the tiniest of clues.
Fillion doesn't see why a best-selling author can't be a larger-than-life character, breaking the expectation of the quiet, studious observer.
"I think Castle is really cool but he doesn't know when to shut up," says Fillion.
"He just doesn't have this filter that says, `Maybe this is going too far, maybe it's not a joke right now'.
"He doesn't have that and that's a flaw.
"And I think people enjoy watching flawed characters."
When not solving crimes or taking social risks in the dry police offices, Castle plays poker with the likes of real-life writers James Patterson, Sue Grafton, Stephen King and Stephen J. Cannell.
• Castle premieres Wednesday at 8.30pm on TV One.
