♪ but Arthur did find a way to get into the thick of the action.

In 1916, the Foreign Office organized a visit to the French and Italian fronts for him to meet and greet the troops.

♪ [Explosions and gunfire] ♪ [Gunshot] This is the most extraordinary photograph.

It shows Arthur on the front line, and he looks like a soldier in a uniform, but the thing is, this isn't a real military uniform.

It's one that he invented for himself.

Real soldiers had little crowns just there.

Arthur's has got silver roses instead.

On the one hand, this is funny, you know, dressing up as a soldier, but actually, I find it sad and desperate.

He just can't accept that he's too old and they don't want him.

♪ The person who would motivate the troops wasn't Arthur himself.

It was, of course, his detective.

Yet again, Arthur found himself playing second fiddle to a phantom.

While Arthur was at the front line, he had lunch with a top French general, who said to him, "Oh, Sherlock Holmes, is he a soldier in the British Army?"

An expectant hush fell across the room.

Everybody wanted to hear the answer yes, but Arthur was forced to say, "Um, no.

He's too old for service"... ♪ [Explosion] but as things got worse, as the casualties mounted, he began to think that maybe, yes, Sherlock Holmes could play a part in the war.

♪ Fans were desperate for a new Sherlock story, and Arthur saw it as an opportunity, a chance to tear up the formula of the classic whodunit and give Sherlock a new role.

♪ This is the result-- the story "His Last Bow."

It's not actually a detective story.

It's a spy story.

Sherlock Holmes comes out of retirement, and, at the personal invitation of the prime minister, he becomes a secret agent, and he infiltrates a German spy ring.

It's rousing stuff.

It's basically British wartime propaganda.

♪ Readers got a Sherlock who would help them win the war, and Arthur got to write something more challenging.

♪ "There's an east wind coming all the same, "such a wind has never blew on England yet.

"It will be cold and bitter, Watson, "and a good many of us may wither before its blast.

"But it's God's own wind none the less, "and a cleaner, better, stronger land will lie in the sunshine when the storm has cleared."