Imagine that Percival and Newt are attending a ball or something where they can't recognise each other, or maybe they do not know the other is attending. So they both meet this charming person and feel like they're falling in love again except that they're married? So they're really scared they're cheating on the other until their identity is revealed to each other. They have this 'are you cheating on me...with me?' moment until they realize that they will always recognize each other.