much in love, makes that late night drive from denver to pueblo, colorado, to visit her boyfriend donthe lucas>> pregnant woman who vanished. >> she was eight weeks pregnant. >> she was last seen in pueblo. >> reporter: when kelsie's family reaches out to donthe, they say he seems oddly unconcerned. >> and i just said, if you hear from her, you need to tell her that we're taking this very serious and that we're calling the police. and so he was like, "okay, i will." >> what did he sound like on the phone? because the call that you're making to him is, kelsie, the woman that you are with, the mother of your child, is missing. we are desperate to find her. >> nothing. no, not worked up. not, you know, just -- >> reporter: he's not scared? "what can i do, how can i help" -- >> no, he just says, "if i hear from her i'll let you know." >> reporter: the pueblo p.d. take over the case. as the last person known to have seen kelsie alive, donthe falls under immediate scrutiny and is called in for questioning. >> how you doing? >> i'm good. >> reporter: he gives a detailed account of what happened, corr