The first two seasons are absolutely brilliant. I just couldn't stop watching. The plots are witty and each episode is so thrilling, the atmosphere is amazing... But unfortunately the quality goes drastically down then... season three is extremely bad and I didn't even finish season four, it is completely unwatchable. The plot doesn't make any sense and it just doesn't feel like THE Sherlock. It feels like the last two seasons were created just because the series became so unbelievably popular and the producers wanted to squeeze out as much money as possible, in my opinion. They are not worth watching at all...