The pressure of having to finish the screenplay combined with the curveball of having to write an entirely new ending was too much for Raymond Chandler. He quickly came down with a severe case of writer's block. According to a near-legendary story, Chandler offered to finish the screenplay by working drunk; in exchange for sacrificing his health to produce the requisite pages on time, Chandler was permitted to work at home (a privilege rarely granted to screenwriters) and was provided two chauffeured cars, one to convey the completed pages to the studio and the other for his wife. Chandler turned the script in on time. Many now believe the drunkenness was simply a ruse by Chandler to wrangle extraordinary privileges from the desperate studio.
When the description of Morrison is given on the radio at the hotel, the only thing missing was the suspect's height, possibly to avoid embarrassment to star Alan Ladd, who was only 5'6".
Just after the fight between Johnny Morrison and the two thugs who kidnapped him, one of the thugs is seen soaking his broken foot in a round tub. That wasn't in the original script; the actor had really broken his foot filming the fight and, without consulting screenwriter Raymond Chandler, director George Marshall rewrote the script to have the character break his foot as well.
The film was rushed into production in March, 1945 without a completed script, because Alan Ladd had been called to return to military service. In 1943, Ladd had served in the U.S. Army for ten months, before being honorably discharged due to illness. However, he recently had been reclassified as 1-A (i.e., "fit for service"), and was due for reinduction in May 1945. This meant that Raymond Chandler was in a rush to finish the script, so the film could be completed in time. In the end, all men aged thirty or over, including Ladd, would be released from the obligation.
Many of the cars in the film have a "B" sticker on the windshield. This is a reflection of the wartime rationing of gasoline. Gas was rationed primarily to save rubber, because Japan had occupied Indochina, Malaya, and Indonesia. There was a shortage of gas on the East Coast until a pipeline from Texas was constructed to replace the transport of crude oil by sea. The B sticker was the second lowest category, entitling the holder to only eight gallons of gas a week.