Fear in the sunlight - Nicola Upson

Summer, 1936. The writer, Josephine Tey, joins her friends in the
holiday village of Portmeirion to celebrate her fortieth birthday.
Alfred Hitchcock and his wife, Alma Reville, are there to sign a deal to
film Josephine's novel, A Shilling for Candles, and Hitchcock has one or two tricks up his sleeve to keep the holiday party entertained - and expose their deepest fears.

But
things get out of hand when one of Hollywood's leading actresses is
brutally slashed to death in a
cemetery near the village. The following
day, as fear and suspicion take over in a setting where nothing - and
no one - is quite what it seems, Chief Inspector Archie Penrose becomes
increasingly unsatisfied with the way the investigation is ultimately
resolved. Several years later, another horrific murder, again
linked to a Hitchcock movie, drives Penrose back to the scene of the
original crime to uncover the shocking truth.