that other matter that needed proving. who did this? >> coming up -- after just a few hours at the house, detectives leave the scene. >> how can you be done with your investigation that quick? >> so the family decides to do a little detecting of its own. >> there was still water in the tub. we pulled the drain. and we saw black scuff marks. >> when "dateline" continues. or...oh! i can't wait to go there! or reunite there, ♪ ♪ start here. walgreens makes it easy to stay protected wherever you go. schedule your free covid-19 booster today.