Well, if it looked like the woman was getting hurt, I'd get involved. First try to talk it down and then get physical to keep the wife safe. If it was a woman beating up a man, I'd get in there and just try to get between them.
It's a non-confrontational way to break the tension.
"I'm sorry, folks, I hate to interrupt, but I'm a bit lost and you are the first people I've seen in 10 blocks. Can you help point me in the right direction?"