DOCTOR WHO IN DETAIL

The TARDIS lands at UNIT HQ and, after introductions, the Doctor asks for UNIT's help to identify a woman who seems to be appearing everywhere he and Ruby goes - each time as a different person. Kate tells the Doctor that UNIT has already started looking into a woman called Susan Triad, an IT genius who is about to release software worldwide for free, a gift from S Triad Technology. The Doctor notices that S Triad is an acronym of TARDIS - and everyone in UNIT has already noticed that as well., which is the reason they have been looking into her. Ruby is more interested in the woman's first name, Susan - the name of the Doctor's granddaughter.

Kate tells the Doctor that Triad Technology was launched, and rebranded as S Triad Technology two months ago. Even without the anagram UNIT got involved when a genius offered to release free software, but investigations have come to nothing, and the software is clean. No secret alien signals have been found.

On the screen in UNIT HQ they can see Susan Triad during a rehearsal, after hacking the link, for the big release at 15:00. Melanie (Mel) Bush is working undercover on the media team. Kate tells the Doctor that Mel has reported that Susan Triad is actually really nice.

The Doctor then tells Kate there is another mystery woman - Ruby's real mother. Morris, UNIT's scientific advisor, wonders if there is woman that keeps appearing, and another that has not been seen, are they the same person. Rose Noble asks the obvious question. If the Doctor has a time machine why doesn't he just go back in time. The Doctor tells her he has been there once, and can't cross his own history - basically time-locking himself out. The Doctor then mentions the snow that keeps happening; that night is so raw and open that taking a time machine back in time is the last thing he should do.

Harriet tells the Doctor that whilst is sounds Dickensian it happened in 2004 and that there was a CCTV camera positioned 66m (almost 73 yards) away in a storage yard. Ruby says she has the footage, on a VHS tape, at home. It's old black and white footage, but with UNIT's equipment they could sharpen the image. Ruby, along with Rose and Colonel Ibrahim, returns home to find the tape. Carla insists on returning with Ruby to UNIT leaving their neighbour, Mrs Flood, to look after Carla's mother, Cherry. Once Mrs Flood is alone with Cherry she enigmatically warns her that a storm is coming in, and that He waits no more.

At UNIT HQ Mel returns with a daily DNA sample from Susan - Sue - Triad, confirming she is still human.

Ruby returns to UNIT with the tape, but is more concerned her mother has been held downstairs, until the Doctor uses his sonic screwdriver to grant her clearance. With the tape the Doctor asks Kate if UNIT has a time window. Despite promises to not experiment wit h time travel Kate admits they do have one. The Doctor laughs when he sees how the time window has been lashed together, and is introduced to head of Time Window Security Colonel Winston Chidozie. Normally the time window doesn't show much detail, but the Doctor says they have much more power with the content of the tape. The Doctor, Ruby, and Chidozie remain inside with everyone else behind protective glass the time window starts to project Christmas Eve 2004, along with actual snow.

Everyone can see Ruby's mother but she wears a hood an no-one gets a good view of her face. Moments later they see the TARDIS and the Doctor arrive (for the first time - see The Church on Ruby Road). The Doctor can remember being there - but his memories are changing. When the woman starts pointing Chidozie goes to investigate what she could be pointing at. Behind them a black swarm appears where the TARDIS and Chidozie had been and starts glowing red. Kate asks if the swarm is a projection of 2004, or is it real in 2024.Chidozie has disappeared, but when Ruby calls for him he tells her he is not in the swarm, but is lost - in Hell. After drawing too much power the time window equipment overloads, and the swarm disappears as the projection ends. They find the body of Chidozie - but it is just dust as though it has been dead for a hundred years.

The Doctor asks Mel to take him to Susan Triad, and they get to her 10 minutes before she is due to make her announcement to the world. The Doctor is trying to determine it Susan is his granddaughter, but doesn't get any recognition from her when he introduces himself and shakes her hand. Susan does tell the Doctor she gets a lot of dreams, but is taken away for her presentation before she can elaborate. As she leaves the Doctor asks if Susan dreams of some of the places he has seen her.

UNIT analyse the video from the VHS video and the tape has changed - now showing the swarm. At the centre of the swarm the see a shape - the TARDIS. Only this is a second TARDIS - something the Doctor said he could never do. Inside UNIT the current TARDIS starts making a loud groaning, and Kate thinks the swarm could still be there - just not visible. Kate orders non-essential staff to evacuate. The Vlinx scans the TARDIS and confirms a life-form. On screen Susan Triad's presentation plays as the TARDIS starts groaning.

The Doctor and Mel are watching Susan's presentation, and over a com-link the Doctor tells Kate to take Ruby to the time window.On stage Susan is struggling with the auto-cue, and starts talking about having bad dreams. At UNIT HQ Kate anounces herself to the invisible swarm around the TARDIS, and Harriet starts talking as if possessed. Kate tells the Doctor Harriet's full name - Harriet Arbinger - or HArbinger. Harriet starts talking of the Toymaker, the god of games, the Trickster, the god of traps, Maestro, the god of music, Reprobate, the god of spite, the Mara, the god of beasts, and the trifold deity of malice and mischief and misery, and finally the mother and father of them all - Sutekh. As the swarm appears around the TARDIS it coalesces into a dog-like create with glowing red eyes.

On stage Susan's face changes as she says she brings Sutekh's gift of death to all humanity. At UNIT HQ Harriet's face has also changed, and in the time window snow falls as the time window shows Christmas Eve, 2004, and the hooded figure of Ruby's real mother.