At all.
I'ld like to point out (since some don't see the idea behind all those numbers between 1 and 10), that 6 is a GOOD score! It means it wasn't great or brilliant, but good enough. And this was.
I read a lot of bad reviews that seems to me they have a problem about it not being 'realistic', like this couldn't happen in the real world. This to me, is not a valid complaint. Not every movie is Schindler's List.
I say this COULD happen, but it's definitely not plausible. But that's why it is a thriller series, not a documentary. It was clearly designed to entertain, and not to be deep.
And entertain me, well it kinda did! The story is a classic thriller concept (which I happen to like), and nothing new at all. But then the way it unfolds, and the places it goes were pretty new to me and just surprising enough.
Definitely not a must see, oh no. But if you're in the mood for this kind of old school style thriller to be entertained, I see no reason why "The Stranger" could not cure that itch.