A house built in 1940 has mice. How do you get rid of them?

This is not about my house which is twelve years old. It’s about someone else’s house. Built in 1940, it has mice inside; the owner does have two cats. The mice run over the beds at night. Is this an impossibility or are there ways to get rid of the mice completely? it’s a two story house that is not in the country but in a subdivision. Thank you.