Is Euros all part of Moriarty's plan for Sherlock?

At the end of the last series, Sherlock resurfaced from a drug-induced fantasy telling us "Moriarty is dead. More importantly, I know exactly what he's going to do next…"

Hmmm… you didn’t really though, did you Sherlock?

In episode one, as a twitchy Sherlock looked out for signs that his arch-adversary’s final game had begun, you couldn’t help thinking that doing nothing, and letting Sherlock drive himself mad over it, had been the plan after all.

When Sherlock was sent a DVD labelled 'Miss me?', for a moment he, and we, thought Moriarty had finally made the “posthumous move” the episode synopsis had hinted at – but no, this was actually Mary’s message from beyond the grave.

While episode two introduced us to a despicable new villain in the shape of national treasure/serial killer Culverton Smith, there was still no hint of Moriarty until the end, when another 'Miss me?' appeared (revealed under UV light), but turned out to be from none other than Sherlock’s long-lost sister.

That was a brilliant twist but it still leaves us wondering, where's Moriarty? When is his posthumous plan going to kick into action?

Perhaps it already has. When he set Sherlock up for a fall at the end of series two, Moriarty had clearly done his homework on the detective so it's impossible that he didn't know about the family secret, Euros, the wayward Holmes sibling.

The last we saw of her, she had apparently pointed a gun at John Watson's head and pulled the trigger, so whatever her deal, it seems she's certainly of the criminal persuasion.

We also heard from Mycroft, in the trailer for finale The Final Problem, that Euros's significance to Sherlock goes beyond simply the fact that she's his sister.

"Every choice you've ever made, ever path you've ever taken, the man your are today, is your memory of Euros."

How could Moriarty resist weaving her into his plans for Sherlock, perhaps even placing her at the heart of them?

I don't think we've heard the last of Sherlock’s nemesis, and it's possible that latest 'Miss me?' may have been a message from Moriarty after all.

Sherlock: The Final Problem is on Sunday 15th January at 9pm on BBC1