In the documentary "Tell Them Anything You Want: A Portrait of Maurice Sendak" (2009), Sendak describes his awareness in 1932 (around age 4) of the sensational Lindbergh baby kidnapping case, including a newspaper photograph of the child's remains. That experience showed him the mortality and peril of children, which the adult Sendak has expressed in many books. "Outside Over There" draws more specifically from the Lindbergh case. A child is stolen from its crib through a window, accessed by a ladder, and one of the illustrations of the lost baby is a deliberate portrait of the infant Charles Lindbergh Jr. The theme of a protective sister is drawn from Sendak's own childhood, in which his older sister was his primary caregiver and devoted playmate.