Traded from Pittsburgh to Chicago in 1957 after his first full season, Walls struggled at times but hit for the cycle on July 2. In 1958 he hit .304 with 24 HR and 72 RBI, his best season, and hit three HR in a game on August 24. After a disappointing season in 1959, he shuffled from team to team. Walls was a batboy for the Pacific Coast League Padres in the mid-1940s. Cubs fans nicknamed him Captain Midnight because of his oversized, wire-rimmed glasses.