What I remember is this:
There is a couple who meet up at the start of the film and it seems like they haven’t seen each other in a while.
The go on a sort of holiday where they encounter a series of people and mess with them/ruin their lives.
For example they convince a married couple into swinging with them, by at the last minute stop it from happening and shame them.
At another point the woman pretends to be a woman with dementia’s daughter and tells her lot’s of terrible things.
I think the film ends revealing that they aren’t married to each other but just meet up once a year to do this to people.