When you arrive, you notice there is only one car parked in the driveway and it's not the van. As you approach the door your backup arrives and you just signal him to hang out. When the girlfriend comes to the door, you give your standard "check on the well-being" speech and wait to see what she says.
She tells you that he has been very distant lately and has been in and out of the house for several weeks. She fears the worst and suspects he has gotten himself involved with some young floozy. She starts talking about a possible mid-life crisis and that at her age she is not too worried about it and says if he wants out, all he has to do is tell her. It's her house so he would be the one to move out as he doesn't appear in any paperwork. She seems very matter of fact and resolved that it might be over. You notice she doesn't seem too worried about anything, least of which is her boyfriend's well-being. You ask a few more questions and then ask if you can go inside and look around the house. She agrees and gives you a tour.
The house is very clean and you notice the living room looks like it's been recently painted. She tells you that on her days off she likes to fix up the house and that she had just painted the room and installed new carpet. You ask her to call the boyfriend, and when she does there is no answer. You ask her to have him call his family member when he gets back or the next time she hears from him. You don't find anything suspicious other than her cool demeanor about his being gone.
While you have been inside, your partner has taken the initiative and asked the neighbors a few questions. They have seen nothing suspicious but do tell you there have been some interesting arguments over there. They haven't seen the boyfriend in several weeks nor has his van been parked there. You are not convinced that this is just about a new romantic interest, but at this point there is not much else you can do. You and your backup leave to handle other calls.
Around midnight, your partner calls you back over to the residence. He said something was bothering him so he decided to double-check the driveway and street. He tells you he has found what appears to be a couple of drops of dried blood but is not sure.