With subtlety and imagination, an illustrator of notable talent embellishes his two themes. Walking along a street--rendered in grisaille with points of interest (like vehicles) in bright color (cf. Sis's other counting book, Waving)--Mary buys flowers and then returns to her building. There she takes the elevator, with a stop for an additional, gaily costumed passenger at each floor. By the time the elevator reaches the 12th floor, both cardinal and ordinal numbers have been rehearsed, the elevator contains people dressed in ten basic colors, and there is a mystery--where is everyone going?--happily solved when it turns out that this is a surprise party for Mary's mother's birthday. The delicately drawn backgrounds contain dozens of clever details to discover. Delightful.