How can I mislead my players without straight up lying?

/r/DMAcademy removed my original post because I mentioned I am a first-time DM, so reposting here to hopefully get some actual discussion...

First time DM here writing my very first very basic one-shot to introduce my wife & some friends to the game. The backdrop is that the players are exporing a haunted house. Their town has higher than average missing persons in the last 50 years since the house was abandoned, and they are investigating why. I want the implication of the exploration through the house to be that the bad guy has been kidnapping people throughout the years and stealing their life-force to extend his own life. However, upon actually meeting the bad guy, it turns out that the life-force is actually used to keep his sick wife alive (just barely). After his little monologue exposition dump he will attack the players to try to takeover their bodies Get Out style since the life-force stealing isn't working well enough.

Do you have any tips about how I can convey this story and successfully mislead the players without straight up lying? Other than the bad guy and his minions (that can't speak) there will be no NPCs because I wanted to be very light on the role-playing side for this first time. Because of this I was thinking that they would come across documents and research about life extension, which I think can lead the players to connect the missing people in the town with the BBEG, but how can I make sure they think he is trying to extend his own life? But I also don't want the wife 'twist' to just come out of nowhere.

Any other general first time DM advice is appreciated as well.