The Debt by Roberta Kray
After eighteeen years inside, Johnny Frank is coming out of jail with just one thing on his mind -- to kill the man who put him there. But his plans soon go dramatically awry. As his past returns to haunt him, a vicious murder and kidnap force him back on the streets of London. He could choose simply to disappear -- if it weren't for Simone.
Through her marriage to Reggie Kray, the author has a unique insight into the inner conflicts of a long-term prisoner, and just as Roberta's life was irrevocably changed by meeting Reg, so Simone's will never be the same again after she enters Johnny's dangerous and unpredictable universe.