The Doctor

Curious about who Clara Oswald is, after locating her in the previous story ("The Bells of Saint John"), The Doctor decides to learn more about his new travelling companion and travels back in time to observe her past. There he discovers that her parents met by a chance encounter caused by a gust of wind blowing a leaf into her father's face who is then rescued, from being run over by a car, by a woman who would become his wife and Clara’s mother. The Doctor then discovers that Clara’s mother died while she was a teenager – both events explaining the importance of the leaf that he found in Clara’s book.

Arriving back in current day earth, on the day after he left Clara, The Doctor takes her to the inhabited Rings of Akhaten, a series of planetoids orbiting a gas giant one of which has a shining pyramid on it. After observing the spectacle of all the rings The Doctor takes Clara to a marketplace full of aliens. There Clara witnesses The Doctor conversing with the locals. Clara however, encounters a seemingly aggressive alien who The Doctor introduces as Dor'een. Dor'een was simply trying to barter a sentimental item from Clara in return for her wares. The Doctor explains that sentimental belongings are used as currency in the market - the more beloved the item, the greater it is worth.

Clara then finds herself separated from The Doctor and while trying to find him she encounters a little girl but she runs away as two men approach asking Clara for the Queen of Years. Curious about the frightened little girl Clara finds her hiding nearby, and after reassuring the child that she means her no harm, they escape after encountering some sinister masked beings.

Clara Oswald

The little girl eventually reveals to Clara that she is Merry, Queen of Years and that she is hiding because she is supposed to sing a song at a ceremony and she is afraid to get it wrong because she must perform this important song in order to keep a malevolent god, that she refers to as 'Grandfather', asleep. Clara convinces Merry that all will be okay and reunites her with her carers so that she can attend the ceremony.

The Doctor then finds Clara and they both arrive at the ceremony where The Doctor explains that since the rings were settled there has been a constant song sung to keep the angry god asleep. The people fear that the god will awaken and consume the entire universe if the song is ever interrupted. Merry then starts singing, joined by a chorister at the pyramid.

Inside the TARDIS

However, during Merry’s song a mummy, in a glass case inside the pyramid, begins to awaken. Merry panics, believing she has made a mistake in the song. A beam of light from the pyramid then envelopes Merry and takes her to the pyramid, where the door locks behind her, trapping Merry and the chorister inside with the mummy.

The Doctor and Clara run off to find Dor'een so that they can rent a space bike. Clara reluctantly sells her mother's ring as The Doctor is unwilling to part with his sonic screwdriver. They take off to rescue Merry and soon arrive at the pyramid where The Doctor uses his sonic screwdriver to gain entry. Inside they discover the chorister attempting to lull the mummy back to sleep by continuing to sing. However, it does not work as the creature begins to stir.

Realising that the mummy is struggling to escape the glass case, so that it can consume Merry's soul, Clara attempts to persuade a distrustful Merry to leave with them, but she seems determined to sacrifice herself in order to placate the god. The Doctor explains to Merry that she doesn't have to sacrifice herself and that throwing her life away would be a waste.

The Doctor and Clara

The Mummy then wakes up and summons the masked beings, revealed by Merry as the 'Vigil', a taskforce that ensure the success of the ceremony by making sure the sacrifice of the Queen of Years happens if it is not done willingly. The Doctor, using his sonic screwdriver, manages to hold the Vigil at bay long enough to let Clara and Merry escape from the throne room. But then as The Doctor makes his escape from the throne room the glass case shatters and the mummy breaks free of its prison and emits a beam of light that penetrates the giant planet.

The Doctor then realises that the mummy was never the god, but rather the god's ‘alarm clock’. As the planet glows red, and a sinister skull-like face appears on its surface, it is revealed that Akhaten is a planet-sized parasitic creature. On discovering this The Doctor orders Clara to take Merry to safety while he confronts the creature. He has realised that it feeds off of memories, stories, and feelings, and so tries to overfeed it by offering the sum total of his Time Lord memories.

While The Doctor has his memories drained, and Merry sings to pacify the God, Clara realises that she needs to help The Doctor and so returns to the pyramid to discover that The Doctor’s memories by itself is not going to be enough to satisfy the creature. She therefore offers the creature the leaf that blew into her father's face on the day he met her mother. The leaf contains an infinite amount of untold potential that Clara's mother never saw because she died early. The creature, overwhelmed by the infinite potential it has consumed, implodes on itself and the planet and the rings are saved.

The Doctor then returns Clara to her home on the same day they left and gives her back her mother's ring. He tells that all the creatures that she saved wanted her to have it back. Suddenly Clara remembers seeing The Doctor at her mother's funeral and asks why he was there. He tells her that she reminds him of someone who died, and she rebukes him for using her as a replacement. As Clara exits the TARDIS The Doctor tries to assure her that he was not using her to replace his friend.