Deadly Isolation (2005)

Crafty Patrick Carlson and his violent accomplice Kyle Mumford have hidden in the woods up north for months after pulling off a major diamonds robbery in San Fracisco. They hoped to collect the loot from a third accomplice, who says it must be with Susan, the widow of professor Ron Mandaway, who probably hid it before committing suicide. Patrick adopts the false identity of Jeff Watkins, a retired entrepreneur, who supposedly had a yachting accident, so she'll take him into her luxury island villa. Jeff's charms win her confidence, but can't find the diamonds, and she seems unaware. Kyle loses his patience, and local sheriff Kirby Grantham, who regularly pays Susan a friendly visit, becomes a problem when his deputy finds Jeff's identity most suspicious.