The renowned underground cartoonist and creator of the Zippy newspaper strip has written and drawn his first long-form graphic novel - a memoir that poignantly recounts his mother's secret life in the 1950s and '60s. 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." Invisible Ink unfolds like a detective story, alternating between past and present as Griffith discovers the holy grail of his mother's past: her diary, an ecstatic evocation of her sexual liaison, and an eloquent testament to her deepest feelings; and an unfinished novel that parallels the trajectory of her own life. Griffith puts the pieces together and reveals a mother he never knew.