When you think of Frank Sinatra’s films, it is easy think about his breezy MGM musicals, the big-budget home movies co-starring his Rat Pack cronies, or his occasional forays into heavy drama (most notably “From Here to Eternity” and “The Manchurian Candidate”). The 1968 drama “The Detective” is rarely recalled when revisiting Sinatra’s cinematic canon, which is a shame because the star gives an uncommonly strong performance in a film that broke considerable taboos with its subject matter and its often incendiary dialogue. “The Detective” finds Sinatra as NYPD Sgt. Joe Leland, who has achieved celebrity status in the tabloids thanks to his ability to crack high-profile mysteries. His latest assignment involves the murder of a son of a prominent businessman. The killing is uncommonly vile – the victim’s skull was fractured and his penis was cut off – Leland’s initial investigation of the crime scene offers evidence that victim was gay. While Leland expresses no animosity towards gays, his fellow officers are revolted by anything relating to homosexuality. As the investigation proceeds, Leland is balancing his own emotional tumult with the collapse of his marriage to a college professor (Lee Remick). The fragility of his personal life stands in stark contrast to the solidity of his professional work – especially when he tracks down the suspected killer and brings out a confession that leads to the man’s death in the electric chair. Having gained a promotion for his detective work – a feat not that is not appreciated by many of his colleagues in the police precinct – Leland begins to pursue a previously closed case regarding the suicide of a CPA. But as he looks deeper into this case, a very serious problem regarding his handling of gay man’s murder unexpectedly surfaces. “The Detective” took advantage of the new permissiveness in Hollywood following the demise of the Production Code, and it was among the first films to receive an R rating when the MPAA introduced its ratings systems. The film’s willingness to offer a degree of sympathy to the pre-Stonewall gay culture – not only in Leland’s progressive attitude, but in detailing police harassment of gays and the disenfranchisement of gay men from the wider society – was highly unusual for a film of this era. (Sadly, the film also included some flashes of the then-prevalent stereotype of gays as emotionally unbalanced and recklessly promiscuous.) “The Detective” also provided an unexpectedly brutal consideration of race relations – when the police precinct is briefly invaded by black radicals, Sinatra’s Leland launches into a stark denunciation of the social burdens faced by African Americans and the role of the police in ensuring this community remained in a permanent state of second-class citizenship. But even more unusual was the role of a new black detective (Al Freeman Jr.) as part of Leland’s team. While this man’s race was never openly considered, his quick embrace of the violent crassness of the police procedures and Leland’s furious denunciation of his behavior stood in stark contrast to the “noble Negro” image that many Hollywood films were peddling at the time. Sinatra surrounded himself with great talent on camera (Ralph Meeker, Jack Klugman and a then-unknown Robert Duvall as his fellow cops, Jacqueline Bisset as the widow of the suicidal man) and behind the camera (Abby Mann wrote the unusually literate screenplay, Joseph Biroc’s cinematography effectively captured the seedy side of the Big Apple, Jerry Goldsmith’s inventive score balanced jazz and angst). Of course, Ol’ Blue Eyes couldn’t resist the cry of cronyism and found places for a few of his pals on screen, but comic Pat Henry and boxing great Sugar Ray Robinson can barely be noticed in their respective small roles. For directing duties, Sinatra tapped Gordon Douglas, a B-movie veteran who belatedly graduated to bigger budget work and helmed Sinatra’s frothy features “Robin and 7 Hoods” (1964) and “Tony Rome” (1967). Douglas was a prolific director, but his output was mostly undistinguished and erratic – his best known work was the giant ant film “Them!” (1954), which he created after shooting Sinatra and Doris Day in “Young at Heart.” For “The Detective,” Douglas hit his mark and offered a crisp, fast-paced and richly cynical drama that presented the ugly side of the NYPD with a brutal intelligence. The power of his direction is so strong that one has to wonder where his career could have been if he had the better luck to score assignments on higher quality flicks. As for Sinatra, “The Detective” reaffirmed his charisma as a film star and his deep talent as an actor. He embodies the film’s shifting moods, barely concealing his contempt for the police corruption around him and treating his shaky marriage with a mixture of crudity and confusion that speeds the union to disaster. In the film’s devastating conclusion, Sinatra offers a subtle portrait of a man who tries a bit too hard to retain his cool when he realizes he was nowhere near as smart as he imagined himself to be. It is a devastating moment that is played in a perfect pitch. Other actors would have gone in for the externalized kill, but Sinatra internalizes his defeat and, thus, creates a greater sense of loss and rue. It is a startling performance in a disturbing film that, strangely, never became embraced as a classic.