Boys of San Joaquin — D. James Smith

Paolo calls Rufus "a Mack truck with no one driving." Rufus is the O'Neil family dog, and he shows up one morning with part of a twenty-dollar bill in his teeth.
Twelve-year-old Paolo figures that there must be more where that bill came from, and since his cousin Billy needs to repair a bent wheel on his bike, there's a reason for looking. Soon Paolo, his brother Georgie, and Billy end up in the monsignor's garden behind the Cathedral of San Joaquin, but it's not exactly treasure they find, it's a hand that shoots out of the undergrowth to grab Paolo's neck. The search for the stash leads the boys -- sometimes scared spitless -- on many a byway around Orange Grove City, California, in the summer of 1951. And onto the byway of conscience.