"Lessons" by Jeremiah Healy

Private Eyes ed. Mickey Spillane and Max Allan Collins, Signet, February 1998, p. 294–314.

For years, the day after Labor Day was traditionally my first day of school. Apropos of that, this story finds the late Jeremiah Healy's Boston P.I., John Francis Cuddy, hired by cancer-stricken World War II veteran-turned-teacher Joseph Vogel to find his thirty-five year-old son, Keith.

After hearing Joseph's other children have died, Cuddy takes him at his word he wants to make amends with Keith before it's too late. Cuddy discovers Keith is a drug dealer and reluctantly tells Joseph, who delivers a surprise of his own.