Without a Trace 4x01

[oceana]

I don't really know what' s going on, but the episode was good, and I might give this show a second try. The only thing that really confused me was the blond girl at Martin's bed in the end.
See, I've only seen a few episodes from the first season, but I do remember that Martin was together with Danny back then. In fact, my memory is very clear on that.
It was also very clear from the way Danny said "Martin" in a broken voice when he saw that Martin had been shot.

So, what's the blond girl doing there? Is she his siser? Ex? (as in so long ago he almost doesn't remember-ex). Some hot chikc who has a crush on him that will never be answered?

Somebody better explain this to me. I don't want to start watching this show if Danny and Martin don't stay together.