"Fifteen minutes after Bill Griffith's father died from a bicycle accident in 1972, his mother turned to him and said, "If I don't tell you this now, I'll never be able to tell you. I had a long and happy relationship with a man you knew slightly." Thus began Griffith's journey to reconstruct this hidden relationship between his mother and a deeply cultured jack-of-all-trades cartoonist and crime novelist. Invisible Ink unfolds like a detective story,...