Frightfully rich and awesomely respectable, the McKells had never been touched by scandal. At least, not until Dane McKell discovered his father's secret affair. Determined to protect his mother, he forced a meeting with the other woman.
But Dane didn't count on falling in love with her himself. Nor did he count on the front page murder that engulfed them all.
Sheila, exotic young international leader of haute couture,is found murdered in her Park Avenue penthouse. Two floors down, the distinguished middle-aged millionaire--Ashton McKell--is hauled off to jail. Next to go, Lutecia, his shy patrician wife. And then--Dane, their handsome, sensitive son. Together, a triangle of murder suspects. Ellery Queen, immobilized, can trick the police into becoming his "legmen" if he discovers The Fourth Side of the Triangle before the blackmailer squeals.

Dane McKell, millionaire socialite, was planning an exhilarating summer when he discovered to his horror that his father was having an affair with another woman. The McKells were not only very, very rich, they were also very, very respectable, and Danes mother was a gentle and lovely lady.
Dane forced a meeting with the woman in the case with the full intent of breaking up his fathers relationship. Then, helplessly, he himself fell in love with her. After thatmurder.
This is the basic situation, a brilliantly plotted detective story that only the old master, Queen, could devise, and that only Ellery, working with his father, Inspector Queen, could solve.
As always with classic Queens, the reader will have it solved three times before he discovers that he has been outwitted as usual.

Well written, fast-moving story with plenty of surprises. The characters are very well drawn and seem to interact very naturally,  almost letdown for the true fan since Avram Davidson completed the manuscript of this Ellery Queen novel, in late April 1963 based on a 71 page Dannay outline subsequently revised by Lee and Dannay. 'Times are changing' with probably one of the most 'explicit' on the subject of sexual content. Ellery seems content in his non-marital status and even got past his usual shyness when he almost asked his nurse on a date.
I'm still not quiet sure if Sheila is depicted in a kind way (career woman) or as a (man-eating) shrew. In 1999 she would have been the first while in 1965 it must have been the latter. The first solution is great. Almost to prove Ellery is fallible a second solution comes to the surface. Not depending on Ellery's cunning abilities but rather on the Inspector's talents. This disappointing 'deus ex machina' is not in keep with the rules of fair-play and is given only a few pages...
It is no surprise that, American public's fondness for courtroomdrama in mind, a simplified TV-Movie was made "Ellery Queen (TV pilot" (aka "Too Many Suspects").
Despite the ghostwriter some typical 'Queenian' references are made to 'Queen favorite writers' as Chesterton's postman is mentioned as are E. Phillips Oppenheim* and Conan Doyle. It surely isn't the first time some criticism crept into the novels and this time, I feel, no exception was made when the rich Dane McKell says: "... A lot of writers have to write stuff they loathe, just to keep the fuel pump running..."

The story unvoldes itself in New York 'in the middle of the 20th century' more than likely between the (hot) summer of 1963 and January 1964.
Ellery went up to Wrightsville in the Mahoganies where a movie outfit was shooting some winterscenes with a camera on a bobsled, which ran into him. After the ski accident Ellery was treated in the private pavilion of the Swedish-Norwegian Hospital in Murray Hill. The 'genial' Dr.Johanneson treated Ellery's legs which had been put in casts. A technique Dr.Johanneson had invented reducing our hero to a 'wheelchair detective' who had to be hoisted in and out of bed. Contrary to what one would now expect he had to stay several months in hospital.
The gray-haired detective Pigott ('Piggie') and detective Zilgitt, who looked like Sugar Ray Robinson, aided in the case. They were assisted by detective Mack of the 17th precinct.
As did the ever present Sergeant Velie, " the tall one with the sledgehammer hands and the rumbling voice.." Inspector Queen is very tolerant of his son's wishes which sometimes  stretches our believes. No Prouty, no Djuna (no West 87th!), no Nikki (although Judith 'Judy' Walsh comes close to the character). No pince-nez, no Duesenberg and no cigarettes (which had to be a problem in light of his smoking habits and the lengthy time he spend in hospital).

*E(dward) Phillips Oppenheim, (1866 - 1946) the prince of storytellers, wrote 115 books and 39 anthologies, and became famous with 'The amazing quest  of Mr. Ernest Bliss'