First 2 seasons are great (exept the ludicrous Season 2 Finale) then it goes down hill from there.

Benedict Cumberbatch put in an OUTSANDING performance throughout.

The Moriarty character here was terribly portrayed and acted. There is No actual intimidation or any level of threat you can sense out of the character / actor. This character could have made this series a full 10/10.

Then the sister garbage twist in the last season. Absolutely rubbish and lame writing. It felt the writers thought that the audiences are a bunch of idoits by adding her to the natrative in such over the top manner.

The good episodes are all of Season 1, Season 2 Episodes 1&2 and Season 3 Episode 2.