Harper is a cynical private eye in the best tradition of Bogart. He even has Bogie's Baby hiring him to find her missing husband, getting involved along the way with an assortment of unsavory characters and an illegal-alien smuggling ring.
Stands and falls on one's attitude to Newman's impersonations and general persona throughout the film, and, indeed, the film seems to be too in love with Newman qua actor to let anything happen. Whilst Newman is obviously famous, the level of 'star quality' that's required for this kind of vehicle hasn't lasted through into 2022, so it lands very strange today, leading your subconscious to ask: "why is he being indulged so much?"
The comedic turns don't fit with the surrounding technicolor—cum—noir aesthetic, and ends up as misfired attempt to distance itself from the black-and-white classics. The fingerprints of the (far superior) Bond franchise seem to be over this as well: wisecracks and fantastic locations plus a physically invulnerable henchman and reckless driving of a sports car. And not to mention Newman's coldly aggressive sexual advances toward (who is almost too 'conveniently' his wife) that the film's tone rewards.
