Introductory Computer Science (CS) for undergraduate students is a course with reportedly disappointing results in terms of student performance, across multiple institutions. Several existing studies have investigated the reason why students drop out of this course. This study conversely explores the experiences of students who have stayed in the course, focussing on students' autobiographical stories about their early experiences with learning CS, in an effort to identify what attracts and retains students in the field. Through semi-structured interviews with twenty-three students in a research-intensive North American university, four factors of motivation were identified: (1) exploring/experimenting within CS projects, (2) social interaction/guidance, (3) real-world applications of CS, and (4) extreme feelings of satisfaction. Based on these findings, CS educators are invited to incorporate opportunities for students to experience these aspects of learning within CS education.