Sam and Malcolm. Malcolm and Sam.
Sam is a cipher. That’s the word that immediately comes to mind when I think about her. She shows up first in 103, and then in various episodes all the way until the end, but in those seven years, the only piece of personal information we learn about her is when she and Malcolm are walking into the office together at the beginning of 402, and she says she and some unnamed, gender unspecified person, got a table at a trendy restaurant. Other than that, nothing.
So what do we know about her? Or more specifically, her and Malcolm, since almost everything we do know about her comes, by necessity, from how they interact with each other.