The most disturbing / tragic episode of your choice

I found the second episode "Not with Kindness" an all round tragic and depressing episode.

Strange thing about the death of Barnard, we just watched the very first episode of season 1 and we see Barnard for the first time. The story is the one with the old guy who years earlier tried to rob his own bank. He's arguing with Frost inside the house and then it shows Barnard outside waiting and we hear gunfire. Barnard rushes inside to find Frost laying unconscious on the floor. The old man had knocked him out, gone upstairs Too shoot himself and his wife.
Later when Frost hears what Barnard did with rushing in after hearing gunfire, Frost says that he could have gotten himself shot doing that. And that's exactly how Barnard dies later.

I'd say the first ever episode is a very powerful tale.

****SPOILERS HENCEFORTH****

During this episode, there is the onoing subplot of Jack caring for his terminally-ill wife, a situation which is obviously affecting him a great deal. A little girl goes missing and is found dead. To top it all off, a skeleton is uncovered with one of its arms hacked off and a bullet hole in its skull. As Jack investigates he unmasks the killer, who has also brutally murdered again and who up until then seemed like the most harmless person anyone could meet. The flashback to the original crime shows a cold, callous and calculating killer. Once his cover is blown, he pulls out the same gun he used to kill the two other men and goes up to his own teminally-ill wife's bed and proceeds to kill her and then himself. The person who is responsible for the little girl's death owns a large number of cats which he/she subsequently kills because they claim there would be no one else to look after them once they are sent down.

And then, of course, there's the deeply moving speech that Jack gives after his wife's death outlining the situation between them in the run up to them dicovering her illness and how they subsequently dealt with it. It's also in this speech that Jack recounts the incident which won him his George Cross and it is really saddening when you realize that he approachedthe gunman fully expecting and even hoping that the madman would kill him.

****SPOILERS END****

I honestly don't believe I've ever seen a greater beginning to a successful and well-loved series as this.

Love Me Tender
For disturbingness though, I'd Say Penny For The Guy, Stranger In The House, Widows and Orphans
All of those were to me deeply deeply disturbing

Im The One Your Mother Warned You About!