In Paul Theroux's novel My Secret History the protagonist returns from his travels in the Orient and discovers his wife has had a secret affair. (Who snapped the photo of his wife and child laughing in the park and with what camera?).

After extensive research and nightly snooping in her handbag, he evntually finds a paper note from the anonymous lover in her purse, and after even more extensive research he finds out who the man is, a coworker of his wife.

She says "but you were so far away having fun in romantic places leaving us in boring old London in winter" and he says "I was freezing to death in Mongolia, longing to be home with you and our son."

After promising to do nothing silly, the cuckold tracks the spoor of the other man to a weekend dinner party at the country home of friends, gatecrashes the house, holds up the assembly with a toy water pistol and publicly makes sure the wife's suitor eats the note, then shoots urine from the water pistol in the fellow's eyes, and leaves. Initially the lover believes he has been blinded, and of course he is humilated in front of his friends.

I guess this is a variation on the panda punctuation joke, but the point is that it makes the character, Andre Parent feel much better and his marriage gets back on track, and on subsequent visits to the bank where his wife works he gets as much deference as if he had walked in with a real gun.

(Theroux denied that the events in the novel or the character of the wife bore any resemblance to real persons alive or dead, of course. The book was published in 1989 and coincidentally Theroux and his first wife Anne divorced in 1993.)

Whether this would work for the LW, I do not know. It seems to me that he and his wife need to sit down and have a chat about this. Are these affairs to do with love, or just scratching the sex itch? Maybe they can work out an arrangement of some kind. The grass is always greener on the other side... until you get there.