Bound by a deep loyalty and a shared childhood as orphans, Rosie, Kevin, Gavin, and Nell pledge always to be there for one another -- a promise that each finds difficult to keep.  As they reunite at a film party in London, it is Rosalind Madigan, the angel of the title, who holds them together.  An Academy Award-winning designer blessed with innate goodness, Rosie is troubled by commitments that leave her feeling estranged from herself and her friends: Gavin Ambrose, a Hollywood megastar, a brilliant actor/producer whose personal life is not as successful as it appears; Nell Jeffrey, head of an international public relations firm and Rosie's best friend, a glamorous woman having a secret love affair; and Kevin Madigan, Rosie's brother, an undercover cop in the NYPD Crime Intelligence Division who specializes in fighting organized crime, an assignment that threatens his life.  Into their midst come a dashing French aristocrat and the world's most successful popular singer, two men who disrupt -- and irrevocably transform "the family."