When Will and Summer (Natasha) met at the cafe, Summer announced that she was pregnant. Only she was lying. Turns out she's lied about a ton of things.

The final scene from April's point of view. "If you tell her the story then she'll know," Maya said. "Know what?" Will asked his daughter tiredly. "I can't explain it. She'll just know." And Maya was right. I did just "know".