Calvin asks Meg hard questions about her father's disappearance, a touchy subject in the Murry family. He first repeats the rumor going around town that her father ran off with another woman. He says he knows that isn't true, but then probes Meg more deeply about her father's disappearance. Meg responds that all she knows is that her father had a top secret clearance with the government. Calvin asks if her father might be dead. Meg replies no, or they would have gotten a telegram. However, he has stopped writing letters. Calvin then asks if she thinks that the government doesn't know what happened to her father. Meg admits that's what she fears.
It takes courage for Calvin to ask these questions, because Mr. Murray's disappearance is such a sensitive subject. Meg is hurt, misses her father and is deeply worried about what has happened to him. Calvin shows his maturity in being able to question her on such a sore subject in a way that Meg can accept.