I don't know exact episode titles but I know that NCIS, NCIS: LA, CSI, Castle, Rizzoli & Isles, and I'm pretty sure Elementary have all used that plot line. Again, my memory is spotty at which shows exactly because every time it comes up, I tend to tune out. But my thoughts are, and I'll be gladly proved wrong if…

At least they did have them dating other people that we SAW. I hate when they allude to other relationships where the s.o. is nowhere to be seen.

Don't know if anyone's mentioned this, because those are a lot of comments to read through, but quite frankly I think the laziest writing is the whole Strangers on a Train plot line. Every damn show I've watched so far has used it - except Supernatural. There's too many types of evil in that show for them to resort to…