She's the Drug That I Need

The last time Brian saw Sarah, he found out that she was leaving town and they had one last one night stand. The following morning he found her gone and a positive pregnancy test in the trash can.
Three years later, he hasn't forgotten about her, nor the child he may now have. He's been searching for her, for them.
But when he finally tracks her down, what happens? Is she happy to see him? Is the child his?