The group picked up a hitchhiker (a musician) and drove down a mountain pass into California. Dean told Sal all about his times in California as they drove past different places. When they all arrived in San Francisco, Dean left Sal and Marylou, without any money, to go find Camille. Marylou complained about “what a bastard,” Dean was.
Dean is quick to abandon both the woman he has led on (after already cheating on her and divorcing her before) and the friend he has brought with him all the way across the country. Marylou's response suggests that there is real human cost to Dean's actions, though the novel doesn't dwell on it.