Sebastian Vaughan was a member of Torchwood Three in the 2000s alongside Jack Harkness, Suzie Costello, Toshiko Sato, Owen Harper and Ianto Jones. He was killed by a cortex leech which controlled his corpse before dying itself.
Sebastian was born to Lady Madeline Vaughan and her husband. He was raised at Rockfell Hall and had a nanny when he was a child, whom he hid from under a bench in the chapel. He was only ever scared of the dark and slept with a nightlight on even as a teenager.
He named the family's dog Blücher and was an enthusiastic student of history, particularly the Battle of Waterloo in which his ancestor and idol Major Charles Vaughan had taken part. His lineage was important to him. He was active and played cricket, tennis and rugby and was at one point rugby captain. He also showed a lot of promise as a horseman, but the horses were sold after an accident with one of the grooms. After sport, he would often go straight to Mrs Davies to ask about food.
Sebastian's father worked at Lodmoor Research Facility for the Ministry of Defence before being promoted to Cabinet minister. He wanted Sebastian to join MI5 but arranged for him to join Torchwood Three after learning of the institute. Sebastian wanted to serve his country and came to work under Jack Harkness in Cardiff. (AUDIO: The Vigil)
Career at Torchwood
Sebastian worked alongside Jack, Suzie Costello, Toshiko Sato, Owen Harper and Ianto Jones. Despite this, he felt comfortable accusing Tosh of doing things wrong even when concerning matters that she specialised in. He also insisted that she finish her report on cortex leeches and put it on Suzie's desk despite her having just logged off to go home whilst he was at a rugby dinner with "the chaps".
Sebastian and Tosh went on a mission together to catch a cortex leech. People almost died because Sebastian missed the security meeting and made a mistake. He knew that Tosh had met with Jack to discuss the issue and he himself was called in to give his side of the story. He was afraid that Tosh was attempting to embarrass him in front of their colleagues.
The two went on a similar mission in which they failed to locate a leech. He claimed that the kit that Tosh made him carry merely slowed him down and that it was pointless. Whilst the two were working late, he brought her food from a Chinese takeaway that Ianto had shown him, not realising that she was Japanese and insisting that it was all the same.
At a service tunnel where Sebastian and Tosh were looking for leeches, Sebastian was wounded in the shoulder. Despite saving lives, they failed to capture a leech and he again said that the equipment was unnecessary. He later told Tosh that everybody was bored of her obsession with the leeches and was dismissive towards her, electing to continue shooting practice instead.
Sebastian found Tosh sitting outside of the Hub and told her that she needed to stop being spineless and to trust her instincts more. She visited him on the weekend of his father's birthday to discuss the leeches and gave him a file to read, which he was unenthusiastic about.
An alarm informed Sebastian and Tosh that there was Rift activity and the two left without all of Tosh's equipment due to his impatience. Sebastian was attacked by a leech and could not be saved by Tosh due to the missing equipment, for which he blamed her. He asked for her to kill him but she could not, causing him to berate her and tell her that she was not and would never be Torchwood material. He died. (AUDIO: The Vigil)
Feeling responsible for Sebastian's death, Tosh took his body home. His mother had his body placed in the chapel and lit candles due to his fear of the dark. His parents arranged for a private funeral after which he would be buried on the grounds. However, he was possessed by a leech and left the chapel, killing Roderick, the security team and his dog.
Madeline and Tosh found him in the water at the beach where he called to his mother to join him, allowing the leech to use her as a battery. Although Madeline was taken in by him, Tosh shot her in the leg to stop her from joining him. He insulted Tosh once more before his body was liquefied. (AUDIO: The Vigil)
The dark was the only thing that Sebastian was ever scared of. He continued to sleep with a night-light even when he was a teenager. He was worried about being made a fool of in front of other people and becoming a laughing stock. He was very active and enjoyed cricket, tennis and rugby. He had a voracious appetite.
Sebastian trusted his gut and followed his instincts. When Tosh determined that the leeches were infecting the homeless of Cardiff, Sebastian said that they were perhaps doing the city a favour. (AUDIO: The Vigil)