The official Doctor Who story synopsis for the fourth episode of Series 7, The Power of Three, has been released.

The Doctor and the Ponds puzzle an unlikely invasion of Earth, as millions of sinister black cubes arrive overnight, almost like presents falling from the sky.

But what are they, what’s inside them and most importantly, who sent them? With the international community at a loss, it’s left to the Doctor to unearth who is behind the mystery.

It’s written by Chris Chibnall and guest stars Mark Williams, Steven Berkoff and Jemma Redgrave.

It will air Saturday 22 September.

[via doctorwhotv.co.uk]