It's a few years after her adventures with Peter Pan, and Wendy's all grown up and married. And it isn't very long before she's given birth to a bouncing baby girl called Jane. Right from the start it's clear there's something really special about this girl. That's why it's appropriate that her birth should be described in a golden splash, not ink.
Just how special Jane really is we only find out later when Peter Pan comes to pay Wendy a visit. He wants Wendy to come fly away with him. But as Wendy's grown up—contrary to what she promised Peter—she can no longer fly and so cannot oblige. In any case, Peter hasn't just come to see Wendy; he's come back for his mother, to take her to Neverland. After Jane whizzes around the room in solemn ecstasy, Peter proclaims her as his mother. Jane recognizes that Peter needs a mother, and she is only too happy to fulfill the role.
So, Peter and Jane take off, flying through the open window on their way to Neverland. Wendy's upset to see her daughter leave, but as she's flying away, Jane assures her that she'll return once she's done Peter's spring cleaning. Wendy would dearly love to go with Peter and Jane, but as she's grown up, she can no longer fly.