The Devil to Pay (1937), The Four of Hearts (1938), and The Origin of Evil (1951) roughly fall in Ellery Queen's middle period and are unique in that the setting is Hollywood. Four Walls Eight Windows published these three mysteries in 2000 under the title The Hollywood Murders.
Ellery's deductions are dazzling as usual, despite that Ellery himself sometimes seems out of place, even stranded, in the unorthodox milieu of Hollywood. Ellery encounters classic Hollywood stereotypes from movie stars to film producers to gossip columnists. The plots offer humor, some snappy dialogue, and a few extravagant Hollywood effects (e.g., a murderous pilot commandeers a small plane). I commend Four Walls Eight Windows for printing this collection.
The Devil to Pay (1937): Ellery Queen has been persuaded to rush to Hollywood to assist in writing a major production only to find that the producer is unavailable. Ellery becomes increasingly frustrated as he waits and waits for his first assignment. Fortuitously, he becomes involved in solving a bizarre murder of a hard-hearted, unethical financier. The murder weapon is an Italian dueling sword of the seventeenth century; its tip is coated with molasses and cyanide.
Ellery's remarkable reputation on the eastern seaboard is of little value in Los Angeles. Ejected from a crime scene, he subsequently masquerades as Hilary "Scoop" King, a colorful investigative reporter, to gain access to crime sites and confidential information. While somewhat farcical, this device allows the story to proceed.
The Four of Hearts (1938): In this sequel Ellery finally meets the young Jacques Butcher, colloquially known as Boy Wonder, executive vice-president of production at Magna Studios, and Ellery begins his work on a screen play. Unfortunately, an elaborate publicity stunt for the new production is derailed by a double murder. While the portrayal of the Hollywood film industry may not be entirely accurate, the plot is entertaining.
The Origin of Evil (1951): Thirteen years have elapsed and Ellery returns to a Hollywood that is reeling from the advent of television. However, as Ellery observes, Hollywood's post-mortem may be premature. This third Hollywood mystery reveals a growing list of surrealistic clues, including a dead dog, dead frogs, a poisoned sandwich, and a mutilated leather bound book of Aristophanes. The solution within a solution offered by Ellery is quite ingenious.
If you cannot find a copy of The Hollywood Murders, you might look for paperback editions from the 1970s and 1980s published by Ballantine Books, Signet Classics, and the Signet Double Mystery series. They are all inexpensive. The Origin of Evil is easiest to locate - look for a 1992 reprint edition by Harper Perennial.