Shelley North (Cyd Charisse), a glamorous American living in Rome, is alarmed when her husband Bill goes missing. That same night near Rome’s famous Trevi Fountain, police discover the body of a dead drug smuggler who happens to have in his pocket, Bill’s phone number. Also at the scene is suave if smarmy American playboy journalist Dick Sherman (Hugh O'Brian) who decides to use his past romantic history with Shelley to uncover what looks to be a juicy story. Yet with old feelings reignited Dick unearths a tangled conspiracy that involves treachery, the narcotics trade and a mysterious killer who is not what they seem.
Writer-director Silvio Amadio, who later became a very different kind of filmmaker with steamy giallo Amuck! (1971) and a run of sexploitation films including So Young, So Lovely, So Vicious (1975) before abandoning cinema to join a monastery (!), assembles a sober, mechanical thriller lacking the wild Italian stylistic flourishes giallo fans cherish. He aims for a semi-light-hearted tone similar to the Donen and Bava films though the comedy, centred chiefly on a Franco and Ciccio-like pair of bickering Italian burglars that unwittingly unearth a vital clue, is painfully laboured and skewed towards a Sixties Italian audience. The film wants to come across as playful and witty but Amadio's script with its arch, knowing dialogue, oozes contempt for its bourgeois milieu, flirty and frivolous female characters and smug playboy sophisticates. Another problem is that the plot centres on two very poised, stiff protagonists that seem like throwbacks to an earlier decade. Sadly both Cyd Charisse and blunt, boring Hugh O’Brian (who seems to have been a thoroughly nice guy in real life) lack the sparkling personalities needed to elevate their roles above the stolid soap opera dramatics of Amadio's script.
At the very least Assassination in Rome makes the most of that sumptuous Roman scenery, hitting all the important tourist spots: the Trevi Fountain, Coliseum, even the Cinecitta film studio where Dick happens across the filming of a Cleopatra like costume epic. Later the action switches to Venice and takes in the scenery there. Through it all Cyd Charisse does not get all that much to do besides waft through picturesque surroundings in her elegant wardrobe. Amadio, mistakenly believing his mystery is more compelling than actually proves the case, keeps events crawling at a snail’s pace. Save for one well staged and reasonably suspenseful sequence with Cyd menaced in her chic apartment and the convoluted gender-bending finale. It makes no sense but unlike the preceding one-hundred and two minutes at least proves memorable.