Abby and the Mystery Baby — Ann M. Martin

America's favorite baby-sitters are detectives, too!

When Abby comes home from school one day and finds a baby on her front porch, she's completely mystified. Where did he come from? And why was he left on the Stevensons' porch?

Abby's mom convinces the authorities to let the baby, whom the family dubs Eli, stay at their house while the search for his parents is conducted. Abby's thrilled, but she can't just sit back and wait to see what happens. Abby and the BSC won't give up until they get some answers for Eli!