Sorry, I have to disagree about Tosh's acting - she may not have excelled in this series (possibly because she hasn't had much acting to do?) although I actually like her character.
But we have just re-watched all the previous series of Shetland. In one series Tosh gets raped, and I have to say she brought tears to my eyes. I'm not a mawkish person, I don't normally cry over what I see on TV, sob stories don't get to me. But she did make me feel incredibly sad, not to mention quite sick, and I shed a few tears. I have seen the episodes before, and wasn't looking forward to them, so I suspect they affected me last time too.