David Benscoter spent 24 years mastering his skills as an investigator, breaking cases on bank robberies and political corruption for the F.B.I. and the I.R.S. Now, he’s taking a bite out of a different kind of problem — lost apples. Apples have long been a hot commodity for the people of Washington, but in recent years, many orchards have been left abandoned. As orchards are neglected, many varieties of apples are being lost to culinary culture. Benscoter is bringing them back. So far, the apple investigator has given new life to three lost varieties: the Nero, the Arkansas Beauty and the Dickinson.