Marvin's ups and downs occur on the elevator of ""a big interesting building,"" where he gets separated from his daddy on the way to the dentist. Trusting and inquisitive, Marvin wanders off the elevator and into an office, a fashion show, a gym, a cafeteria. . . and even when he's involved in a fire drill and stuck in the elevator, all the people are ""nice"" and ""friendly"" and forthcoming with donuts or cookies. At last, his arms full of presents, Marvin runs into his daddy, and when they finally get to the dentist she too gives him presents--and pronounces his teeth ""just fine."" It's essentially an uneventful outing, so uniformly, blandly pleasant that it's not as ""interesting"" to read about as to experience--but it certainly offers a positive view of city living.