Hey, Doctor Who is back tonight! Doctor Who is back! This is, of course, a great thing, and although I'm sure you've been eagerly following the show to date, here are five things you should be thinking about before you tune in to "Let's Kill Hitler" tonight. Spoilers for those not up to date on season six so far.

The Doctor Is Dead

Well, maybe that should be revised to a Doctor is dead. After all, we all saw him die with our own eyes in "The Impossible Astronaut," just before we saw an earlier version of him appear with apparently no knowledge of what had just happened. So that's that, right...? Well, not exactly: After all, another Doctor - who appears to be the earlier version of the one that died - turned up soon after the murder, and as we learned in later episodes in the season...

...Appearances Can Be Deceptive

Brand new this season: "Gangers" - Physical cloned avatars of people that are physically identical to them and can be "driven" by the originals without their knowledge. By the end of the last run, we had seen both Amy and her baby be replaced by gangers without anyone realizing it and met the Doctor's ganger who was, possibly, killed in action... except that the Doctor admitted that there was a chance that he might've survived. So could the Doctor we saw die be the ganger Doctor? Or, weirder still, did we see the real Doctor die, and the one we've been following all season is actually the ganger?

Amy Pond Is River Song's Mother

Meanwhile, we've finally learned part of the secret of Doctor River Song, who's been popping up and confusing us since season four... She's actually the daughter of Amy and Rory, kidnapped as a baby and taken through time by forces still unknown who plan on turning her into the perfect weapon with which to kill the Doctor. Currently, all signs point to her succeeding in that mission - We've already seen a young girl who may be a younger River wearing the same astronaut suit as the Doctor's assassin, and River has always claimed that she killed the best man she ever knew... But it gets even weirder, in terms of River's secrets, because...

...River Song May Be A Time Lord

Certainly, the forces that kidnapped her back when she was baby Melody Pond think so, and they appeared to have the medical information to back that up, something that even the Doctor agreed seemed real. Apparently, it's because she was conceived on the Tardis while it was traveling through time... but is that really the case, or is there more going on that we know about yet? (Spoiler: Probably.)

The Silence Are... Somewhere

Meanwhile, we shouldn't forget the Silence in the middle of all of this. An alien race that has been manipulating the human race since it first evolved, that no-one ever realized was there - or, to be completely fair, remembered was there when they weren't actively looking at them - the Doctor seemingly ordered their genocide back in 1969... but they apparently survive until at least 2011 in order to be present when the Doctor died. That makes sense, considering that they seemed to "own" the astronaut suit that the Doctor's assassin wore. Does this mean that the Silence are in league with the humans that kidnapped baby River/Melody in the far future (Are they controlling them?)? And also: Did the Silence cause the destruction of the Tardis in season five? After all, we were told that that was someone connected to the phrase "Silence Will Fall"...

There's no doubt that there are a lot of dangling plot threads left to tie up in the remaining six episodes this season, but given showrunner Steven Moffat's love for intricate storytelling and tightly-plotted reveals, I've got complete faith he can pull it all off. The new run starts tonight on BBC America in the US, and BBC One in the UK, and you can expect recaps here every Sunday morning for the entire thing, starting tomorrow.