When Aric Knuth was a little kid, his dad would leave for six months at a time. He was a merchant marine. And Aric would record cassettes of himself and send them. He'd leave one side blank, for his father to record a response. But he never did, even though Aric asked him to on every tape. Aric talks to host Ira Glass about what it was like to finally ask his dad why. (7 minutes)

Act One. Make Him Say Uncle.

Lennard Davis grew up hearing from his parents that he should, at all costs, avoid being like his good-for-nothing Uncle Abie. Later, after his father died, that very same uncle told him that his father was not, in fact, his father. Instead, he said, Lenny was a product of in vitro fertilization, and he, Uncle Abie, was the sperm donor. At first, the evidence points to the possible truth of Abie's story, then more evidence seems to indicate he was lying. It takes Lenny more than 20 years to sort out whether it was true, and he finds out the answer—definitively—as tape is rolling. (30 minutes)

Act Two. My Favorite Martian.

Paul Tough's father was a mild-mannered professor. And then one day he left his family and went on a quest. In this story, for the first time, Paul joins him on that quest: to make contact with extraterrestrial life. Paul asks his father the questions he's always wanted answered about his alien pursuits. Paul is an editor at The New York Times Magazine. He first read a version of this story at the Little Gray Book Lecture Series in New York. Paul's father has set up a website for extraterrestrials to use in contacting humans: www.ieti.org (IETI stands for Invitation to ExtraTerrestrial Intelligence). (18 minutes)

Song: "Calling Occupants of Interplanetary Craft," The Carpenters