The source for the French detective drama Heads or Tails? was the American novel Baroni by Alfred Harris. Phillipe Noiret plays Baroni, a weary Bordeaux detective, hot on the trail of Morlaix (Michel Serrault). Morlaix's domineering wife has allegedly committed suicide, but Baroni suspects murder. As hunter and hunted get to know one another, an unusual bond forms between them. When Baroni is forced to retire by his corrupt superiors, he accepts a bribe from Morlaix, and the two men retreat to the freedom and comfort of the South Seas.
Source : allmovie.com