aha!
last episode of last season. she was very upset when her young techie was shot and dies. she thought that he felt she wasn't letting him 'stay'. because she was upset, she spent the night at booth's. during the night she went to his room for comfort. need i say more? she tells him that she's pregnant and he's the father. there's a moment when you wait to see his expression. after a lifetime, he finally grins and you see he's overjoyed. he's got another chance with a child.