Hayley Shipton (played by Toks Olagundoye) is a recurring character from season 8 of Castle.
Hayley is brought in for questioning after she's found searching an apartment rented by one of several victims of a shootout, which also apparently involved Captain Beckett. During the interrogation, Esposito and Ryan reveal that she's born and raised in East London, Hackney to be exact; her mother is serving 20 years in prison, though the charge is never mentioned. Hayley joined the Metropolitan Police Force, but was booted out because of her (alleged) "tendency to cut legal corners".
Hayley tells the detectives that she's an independent security specialist, hired by an insurance company to track down stolen Social Security numbers and the hacker(s) who stole them. Five of the numbers popped up as active in New York City, thus her presence in the victim's apartment - apparently he was one of the hacker's customers.
When Castle reluctantly accepts Hayley's offer to help find Beckett, Hayley's one condition is "no cops". As she puts it, "Differing agendas. The cops serve and protect the city. I serve and protect me." She takes time to give Alexis Castle PI tips, which comes in handy later, and at the end of XX the two plan to keep in touch.