One cardboard box plus one girl's active imagination equals an extended jaunt to Grandma's house next door, with a detour into make-believe. On a mission to deliver a gift, the granddaughter uses the empty box to create different modes of transport; Ayres's (Macaroni Boy) economical text (e.g., , the four words "First... car/ then... boat..." unspool over eight consecutive pages) leaves it to Tusa's (The Ballad of Valentine) characteristically cheery gouache illustrations to flesh out the journey. Sprightly spot illustrations show the girl earnestly gathering materials for each imaginary vehicle, and these alternate with spreads of the girl piloting the crude finished product. In the end, she flies her "plane" (a magical from-behind scene features the girl soaring between lawns with an airborne pet chicken, dog and turtle in tow), takes the "subway" and gleefully presents an oversize watering can to her gardening grandma. Tusa's sure lines and sunny hues depict both the girl's diligence and her playful nature. Background details, like a Humpty Dumpty knickknack among the kitchen clutter, add to the story's buoyant, can-do tone. Readers are continually treated to clues as to where the resourceful girl gets her creative spirit, as in the whimsical mailbox her mother paints or the concluding "tea party" Grandma hosts. A clever synergy of art and text, and an invigorating romp into the realm of childhood play. Ages 3-up. (Apr.)