Martha and Donna in “The Sontaran Stratagem”

Donna, do they know where you are? I mean, your family, that you're travelling with the Doctor?

Not really, although my granddad sort of waved us off. I didn't have time to explain.

You just left him behind?

Yeah.

I didn't tell my family. I kept it all so secret, and it almost destroyed them.

In what way?

They ended up imprisoned. They were tortured, my mum, my dad, my sister. It wasn't the Doctor's fault, but you need to be careful, because you know the Doctor's wonderful and he's brilliant, but he's like fire. Stand too close, and people get burned.