The Mystery from Way Back When

It's 1944 and World War II is raging in Europe and Asia.  On the American homefront in the Keighry Head neighborhood of Elizabeth, New Jersey, Irish Catholic brothers Benny and Timmy Finnegan watch from a distance as a young girl abandons a newborn baby in a picnic basket on the steps of Sacred Heart Church.  They realize the baby needs immediate assistance and bring her home to their delightful mother, Claire.
 The only clue to the child's origins is a note found in the basket requesting that she be raised Catholic.  The police arrive to get the baby to the hospital while the parish priest arranges for her adoption.  Meanwhile, the boys try to play detective and figure out who gave the baby up.  Benny even has a likely suspect, Nancy Kilkenny, but she hotly denies it.  Years later, the baby, all grown up, has an urgent reason to connect with Benny and Timmy to try and find out what really happened way back when.
 Who was the mother who gave her away?  What happened on that memorable day in 1944?  And can she ever manage to find out the truth?