The letters of transit first made their way into Rick's Cafe Americain by Ugarte. Ugarte had gained access to the letters by killing two German couriers, and had wanted to sell them to the highest bidder, who would be arriving at the Cafe later. Ugarte had known he was wanted for the murder of the the two German couriers and entrusted Rick with the safe keeping of the letters. Sure enough, he was soon arrested by local police. He later died in police custody without disclosing the whereabouts of of the letters. Rick, the owner of Rick's Cafe Americain, was now also the owner of the letters.
Signor Ferrari, a rival business owner and major figure in the criminal underworld, propositions Rick into selling his Cafe, which he denies. He also suspects that the letters of transit are in his possession, which he discloses to Victor Laszlo. Laszlo was the Czech Resistance leader who had escaped a Nazi concentration camp and wished to escape to Lisbon and then America, with his wife, to continue his work. His wife, Ilsa, had been a former lover of Rick's. Rick and Ilsa were supposed to escape from Paris together, but Ilsa stood him up. Rick had been deeply in love with her and was still bitter toward her for leaving him. Laszlo was unaware of their love affair because at the time he had been detained in a Nazi concentration camp, where he later escaped and hid. During that time Ilsa thought her husband was dead, but later found out he was alive and hiding. Promtly after discovering her husband was indded not dead, she refused to leave Paris with Rick. Rick's bitterness towards her had not depleted over the time the were apart. His bitterness toward her was due to Ilsa not giving him an explanation as to why she left him.
After learning that Rick might have the letters of transit Laszlo meets with Rick in his office. Rick refused him and Ilsa the letters and told Laszlo to ask his wife for the reason. Laszlo never does ask Ilsa the reason, but later becomes aware that there had been a love affair between them.
Accompanying Victor Laszlo's arrival in Casablanca was German Major Strasser. Strasser was to make sure that Laszlo would not recieve the letters of transit. He would do anything in his power to stop it. Captain Louis Renault was in alliance with Strasser, helping him to make sure that Laszlo would not receive the letters of transit. Under Strasser's command, Renault went as far as shutting down Rick's Cafe because of Laszlo's resistance against the Germans, and later arrested him on a petty charge. Renault was not a bad peron, just a corrupt oppertunist. He'd take advantage of situations within Casablanca to help himself and his desires. Such as giving letter of transit to women who would offer him special services.
The young Bulgarian refugee Annina Brandel had gone to Rick asking for help in leaving the country. Although Rick had not given her and her husband the letters of transit, he helped her husband in winning a few hands of poker, which gave them the money the needed to give to Renault. Renault had been less than happy to know that Rick had helped them, which had ultimately taken business away from him. He's rather the services the women offered than the money that they brought in.
Ilsa wanted to obtain the letters of ftransit in order for her and her husband, Laszlo, to escape to America, where he would carry on with is work as the Czech resistance leader. Ilsa would do anything to get ther letters, and he refused. She then threatened him with a gun, but was unable to carry through with her threat, She then disclosed her love for him, and finally revealed why she had left him in Paris. Which finally set him at ease. That rainy day in Paris had haunted him, and now he was finaly at rest, relieving his bitterness towards her. He proposes that he will give Laszlo the letters of transit, which would finally allow him to leave for America, and she would stay with him.
Rick convinces Renault to let Laszlo out of custody in order for him to be exposed and later charged with possession of the letters of transit, and tells him that he and Ilsa would leave for America. When Renault tries to arrest Laszlo as arranged, Rick double-crosses Renault, forcing him at gunpoint to assist in their escape. Rick makes Ilsa board the plane to Lisbon with her husband, telling her that she will regret it if she stayed. Major Strasser then arrives at the airport by himself, he had been tipped off earlier by Renault. When he tries to intervene Rick shoots him. When police reinforcements arrive, Renault tells the men, "round up the usual suspects."
The different discourse communties within Casablanca: Laszlo and Ilsa, Rick and Ilsa, Renault and Strasser, Rick and Renault, Ugarte, and Renault himself, all reveal their reasons and motives in obtainig the letters of transit. For some, the letter were more valuable, and others just a price tag. Either way they all desired the letters, and Rick, probably the most impotrtant discourse community had not gotten what he truely desired, Ilsa.