What is Mr. Martin planning todo when he buys his unaccustomed pack of cigarettes in "The Catbird Seat"?
A lifelong non-smoker, Mr. Erwin Martin's purchase of a pack of Camel cigarettes was an integral part of his plan to murder his nemesis, Mrs. Ulgine Barrows. Martin had decided that Mrs. Barrows must go, and he carried the Camels with him when he visited her West Twelfth Street apartment one evening. While the surprised Mrs. Barrows made him a drink, Martin looked about her apartment for a weapon; he found nothing satisfactory. He had planned to use something from the apartment, but "None of them would do." As for the cigarettes, they would be used to confound Mrs. Barrows and throw off the police.
Mrs. Barrows smoked only Luckies. It was his idea to puff a few puffs on a Camel (after the rubbing-out), stub it out in the ashtray holding her lipstick-stained Luckies, and thus drag a small red herring across the trail. Perhaps it was not a good idea. It would take time. He might even choke, too loudly.
But as Mrs. Barrows entered the room and Martin still had no weapon with which to rub her out, his mind took a new turn. He
... became acutely conscious of the fantasy he had wrought. Cigarettes in his pocket, a drink prepared for him--it was all too grossly improbable. It was more than that; it was impossible. Somewhere in the back of his mind a vague idea stirred, sprouted.
The Camels were originally purchased as a decoy, and Martin was careful to buy them in the "most crowded cigar store on Broadway." No one would remember him buying the cigarettes. Now, he realized, he would smoke them in front of Mrs. Barrows instead of waiting until after she was dead. The cigarettes would provide him a reason to allow her to live; Martin's new plan would simply discredit her, he foresaw. Martin realized that the surreal situation--him drinking and smoking in Mrs. Barrow's apartment--was so outlandish that no one would believe the woman's story. So, with the Camels as a starting point, Martin's bragged to her about the real Erwin Martin: He berated his boss, told her he planned to bomb the office building, and that he would be "coked to the gills" on heroin when he did it. Martin's "vague" plan had "sprouted" fully. He was so boring and predictable that no one would believe the wild allegations Mrs. Barrows was likely to make. Before he left the apartment, Martin left the Camels behind--concrete evidence that he knew no one would believe.