Adrift - Torchwood 2.11

In which Gwen Cooper is approached by her old colleague, PC Andy Davidson, to help him look into the case of a missing person - a boy named Jonah Bevan. Gwen discovers that there have been many disappearances, which she suspects were due to the Space / Time Rift running through Cardiff. On checking CCTV of Jonah's last known movements, her fears are conformed as she witnesses him vanish in a flash of light. Tosh confirms that the disappearance occurred just as the Rift demonstrated a negative reaction - something the team had always put down to the equivalent of an aftershock following an earthquake. The team are used to dealing with things coming through the Rift into the city, but Gwen becomes worried about it taking people away. She approaches Jack for help in investigating further, but he seems reluctant to do so, and advises her not to waste time following this up. Andy then introduces Gwen to Jonah's mother, Nikki, who runs a support group for relatives of missing people, and she sees the scale and emotional impact of the problem.

Gwen becomes obsessed by her investigation, frustrated by Jack's insistence that she forget about it. Her work starts to put a strain on her relationship with Rhys, and things are not helped when Andy confesses that he has always been in love with her, and is jealous of her husband. This is why he did not attend her wedding. Gwen goes to the Hub late one night, and walks in on Jack and Ianto making love. Jack again refuses to help her, but Ianto gives her some GPS co-ordinates - which lead her to Flat Holm Island, which lies off Cardiff Bay. Gwen goes there and discovers a secret Torchwood installation built beneath the island. Here a number of people who have been returned from the Rift are looked after by nursing staff. All have been physically and mentally scarred by the experience. Amongst them is Jonah, though he is now some 40 years older. He was badly burned when deposited on an alien world, witnessing an entire solar system burn.

Gwen decides to take Nikki to visit her son. At first she refuses to believe that this older man is Jonah, but he tells her things only her son would know. As she is about to accept him, he emits a terrible scream, and the staff reveal that he does this for 20 hours every single day - his experiences having snapped his mind. Jack appears on the island and tells Gwen that he set up this sanctuary once he took over Torchwood Three - to care for people who wash up out of the Rift after being taken by it. His view is that the relatives are better off not knowing the truth, which is why he tried to deflect Gwen away from looking into things too deeply. Later, Nikki confirms that this is how she feels. She urges Gwen never to show anyone else the island - and tells her that she wishes she had never been shown what happened to her son. At least now she has some closure, and can pack away Jonah's things from his room, knowing he will never return home. Gwen returns to her flat and is comforted by Rhys as she tells him of her investigation.

Adrift was written by Chris Chibnall, and was first broadcast on 19th March, 2008. It is very much a Gwen-heavy storyline, with a more prominent role for Tom Price's PC Andy.
Unless you count the Rift itself, there is no villain to be defeated, or alien threat to be neutralised. It is simply the story of the human consequences of the world in which Torchwood operates.
A certain section of fandom particularly rates this episode, as it features a Jack-Ianto love scene. They've kissed before, and there has been a lot of sexual badinage between them, but here we have them caught in a shirtless embrace. You wouldn't believe the number of gifs I came across researching this piece, and the sites they led me to.
For such an intimate story, and I'm not still on about Jack and Ianto, there is a small cast, with just the two main guest artists. Playing Nikki is Ruth Jones, who came to fame through her co-writing of (with James Corden), and co-starring in, the popular BBC 3 comedy series Gavin and Stacey.
The older Jonah is played by Robert Pugh, who later featured as Tony Mack in The Hungry Earth / Cold Blood, and had a memorable role in Game of Thrones as the monstrous Craster (who coincidentally met his well-deserved fate at the hands of Burn Gorman's Night's Watch rebels). There are very few UK TV dramas which Pugh has not appeared in over recent years.

Overall, a rather disturbing story, which is quite heartbreaking to watch.
Things you might like to know:

• Flat Holm is a real island in the Bristol Channel off Cardiff Bay. In the past it was actually used as an isolation hospital - for people suffering from cholera.
• It was originally intended that Jonah's scream would be added later, with Pugh miming, but the actor wanted to give it a go himself. His scream then had some additional sound effects layered on top.
• Russell T Davies had been thinking of stopping the series after season two, but this episode convinced him that they should continue, but with more emotional storylines and family dynamics for the characters. This fed into what would become the third season - the single storyline of Children of Earth.
• This episode was triple-banked with two other stories - From Out Of The Rain and Fragments - which is why some of the regulars have so little to do.
• Last, but not least, an entirely gratuitous picture of Ianto, with his shirt open. The handsome devil...