Just say "honey, I'm home".

I'd be surprised to see that I have a partner lmao

I'd back away and go sit somewhere where they both had to pass me once they left the bedroom and confront them then. I don't think I'd go crazy on the outside. I'd probably very quietly tell them both to get out. Once they were out I'm pretty sure I'd go nuts.

There in my bedroom?

In that case, I go in and crazy freak out.

If I'm going to be cheated on it best not be in my bed, and after I'm done with my crazy freak out they can take themselves and those nasty sheets and get out of my house.

Find a gun then go in.