Game of Thrones season 6 episode 5 title leaks - what does 'The Door' mean?

Since season six of Game of Thrones premiered the titles of episode two, three and four have all hit the internet, through both official confirmation and leaks.

Now, thanks to HBO Asia, we have the ominous title of episode five: 'The Door'. There's yet to be any confirmation from HBO US or UK.

Now, episode four’s title is ‘Book of the Stranger’, which has a little bit more meaning and history to it, while 'The Door' could mean almost anything.

Let’s quickly think of some famous doors from Game of Thrones. There’s the Moon Door at The Eyrie: that hole Littlefinger pushed Lysa Tully down in season four. 

With there currently being little reason for any of the main characters to go back to the Eyrie within the next few episodes, this is unlikely to be what the title refers to (unless Sansa decides to head back, something she probably will not do).

There’s also the prominent door to The House of Black and White which Arya waits outside. Could she be kicked out for not training hard enough? 

Is this door a metaphorical door one of our characters will walk through? A door into the afterlife, perhaps? A door back into real life (Jon Snow)?