Puzzle is a Duccio Tessari directed Giallo with a script written with Ernesto Gastaldi (Forbidden Photos of a Lady Above Suspicion, The Strange Vice of Mrs. Wardh, and countless great Spaghetti westerns and Gialli). 

Peter has had a car accident which has left him with amnesia. He is being treated by a psychiatrist in London who introduces him to a man who says he knows Peter. Not recognizing him, Peter tries to find out more when the man pulls a gun on him and is shot through the window of Peter's apartment before he can shoot Peter. Forced to get rid of the body, Peter is disturbed by a telegram delivered to his door supposedly from his forgotten wife, Sara, in Italy. Peter travels to meet her and to regain his memory but fails to recognize her at the train station and is guided back to her by a man who has been following him. 

Understandably pissed at her missing husband, Sara, and remembering his previous scoundrel like behavior, finds it hard to credit that he has lost his memory. Gradually won over by a more sensitive and honest man than the one she fell in love with Sara starts to fall for him again. Peter's shadow, George, turns up to menace Peter and it appears that Peter went to London to do a dodgy business deal and has hidden the merchandise he bought. George threatens Peter and Sara that he'll have to kill them if the merchandise doesn't re-appear as the other party in the deal is on George's tail. Peter starts to have flashbacks of his previous self and becomes jealous of Reinhardt, Sara's consolation whilst he was away. Will Peter regain his old self, and if he does will he be able to save himself and Sara? 

Puzzle is a good well plotted and realized Giallo. It is raised from being an ordinary film by some fine touches by the director who elevates a generic script. The script is full of devices which have become hoary old cliché in mystery thrillers and for fans of the Giallo there is little new here and only some small touches of the outré. Luc Merenda was a beautiful man and Senta Berger looks stunning here too, but Merenda never had a great deal of range to his acting. This works well in a plot where he effectively has to portray blankness as an amnesiac but a more assured actor could have added greater mystery to this role. In fact, this blankness causes the film to be more worried with Senta Berger and she does well in a limited role. 

The bit players of Bruno Corazzari, Anita Strindberg and Umberto Orsini do what you have seen them do in numerous genre films but lend to the film's solid unsurprising nature. The restraint of the film is notable and it is only in the presence of a re-appearing chainsaw and switch-blade and  their eventual use that the film moves from proper thriller into Giallo staples. There are a few action set pieces where Merenda lets his fists do the talking and these are effective without being remarkable. 

The best moments of the film come with some of Tessari's choices around camera movement and composition of the frame. When the villain is revealed, his profile is mirrored to suggest duality and they are frequently shot with items in the way to suggest mystery throughout or to hide their identity. Similarly, the script's lack of originality is used well as homage – such as the housebound detective (Rear Window).  

But given the claims on the box to be a “classic giallo” Puzzle is not as good as classics like Tenebrae or All the Colours of the Dark. It is though a welcome addition to your genre library and a solid entertainment.