This was a superb little series. very intense and claustrophobic in terms of its laser focus on the two families - and yet in the most non-claustrophobic setting imaginable viz the Highlands of Scotland. The length of the series (4 episodes) was just right too and the onion skins of family secrets were gradually peeled away in a manner that gripped one with constant surprises and development but never to the extent of becoming implausible or too frequent as can often happen with such series.
It also gave a thoughtful insight, in a quite subtle way, as to how grief can corrode feelings and situations. The police officer and her situation was also very well integrated with everything else - not so much directly but as another way of showing how important and traumatic secrets can be.
the characters were all well-rounded and there was no-one whom one felt was a flat character - all had their sides and it enabled one to at least partially understand and have a degree of empathy for what they did and what they went through.