The Lost Boy was the fifth and final serial of series 1 of The Sarah Jane Adventures. It was written by Phil Ford and directed by Charles Martin. It featured Elisabeth Sladen as Sarah Jane Smith, Yasmin Paige as Maria Jackson, Tommy Knight as Luke Smith, Daniel Anthony as Clyde Langer and Alexander Armstrong as Mr Smith.

It was comprised of the ninth and tenth episodes of the regular series and saw the reappearance of the Slitheen family. Additionally, K9 Mark IV returned briefly in the second episode.

During this adventure, Mr Smith, Sarah's thus far loyal supercomputer, had his alien origin unveiled, along with the unsettling discovery of his true colours. Up to this point he was operating under a friendly pretext, but the facade dropped to reveal a malicious alien underneath the indiscernible guise. Sarah had him subjected to a computer virus to erase the part of his memory that drove him to hostility. After this, his disposition became genuinely benevolent.

Synopsis Edit

A missing child turns out to be, both visually and genetically, Luke. Sarah is forced to hand him over to the "parents". Heartbroken, Sarah rejects Maria and Clyde, and with Maria's dad threatening to sell the house to keep his daughter out of danger, it seems the gang's adventures have come to an end, whilst Luke discovers his new "parents" are not all they seem — an old enemy has returned, and this time, they are in league with a member of Sarah's faithful team in a plot to bring the moon crashing to Earth.

Plot Edit

Part 1 Edit

Having discovered what Sarah, Maria, Luke and Clyde do together, Alan Jackson threatens to move house again, only to have a change of heart when he sees how upset Maria is. His condition for not moving away, however, is that he is kept up to date on their battles against aliens.

A BBC news report on a family searching for their son, Ashley, missing for five months and last seen boarding the Bubble Shock bus, brings a shock. Ashley looks exactly like Luke. Mr Smith compares their DNA, and confirms that Luke and Ashley are genetic matches. Apparently, Luke was not "grown" by the Bane, but was in fact a kidnapped boy whose memory was wiped. His lack of a navel is explained as the result of its removal by the Bane, who are eggborn and find navels offensive.

Chrissie Jackson calls the police and reports Sarah as a child abductor. As Clyde arrives wanting answers, Sarah is arrested and the police put Luke into the charge of Ashley's parents, Jay and Heidi. Sarah is detained by the police until UNIT intervene and have her released. Depressed, Sarah decides she was wrong to involve children and tells Maria to stay away from her, suggesting that she and her father move away. Mr Smith suggests she take on a case to take her mind off things. She visits the Pharos Institute, a research centre where alien technology is being used to conduct experiments into telekinesis. Here she meets the annoying child prodigy Nathan Goss. That night, Luke's new parents watch television and switch to a channel that glows green. They announce to the Xylok that they have the boy in their possession.

Luke's new parents are very unpleasant. They keep Luke locked up in his room at all times. Clyde cuts school to visit Luke, but Heidi does not let them see each other. She claims that her son is a keen skateboarder, which worries Clyde; he knows Luke has a poor sense of balance and is a dreadful skateboarder. He decides to bring a photo of Jay and Heidi to Mr Smith.

Luke becomes frantic upon seeing Clyde leave the house. He tries desperately to escape. Mr Smith, meanwhile, sends Sarah back to the lab to steal one of their headsets, which he needs to work out Nathan's plans.

Back at Luke's new home, his "parents" are meeting with Nathan, just as Luke is breaking out of his room. He fails to escape, but finds his parents are actually Slitheen. Luke asks how they are not fat, as Slitheen wearing skin suits are known to be, and they explain they are using improved compression field technology. Nathan Goss is Korst Gogg Thek Lutiven-Day Slitheen, a child Slitheen Luke met before, now in a new disguise and looking for revenge.

Clyde gets to the house only seconds after Sarah has left. He takes the photo to Mr Smith, asking if the photo can be checked to see if it is a fake. Mr. Smith tells Clyde it is a fake, and he knows... because Mr. Smith faked it. Clyde is confused, as Mr Smith is the Xylok who has been behind everything. Noting that Clyde is not a part of his plan, he fires a bolt of energy at the boy, causing him to digitise and vanish from the real world, and laughs fiendishly.

Part 2 Edit

Clyde wakes to find himself inside Mr Smith. Sarah Jane Smith returns from the Pharos Institute, having stolen a telekinetic headset. Elsewhere, Maria and Alan go to Ashley's house and, after ringing the doorbell, find nobody home. They investigate around the house and Alan finds a skinsuit. Maria realises the Slitheen have Luke. They return home and find Chrissie there and she says that Alan's computer is acting up. Alan sends Maria off to get tea bags knowing she will go over to Sarah's house. Looking at his computer, Alan gets a message on his computer from Clyde, who states Mr Smith has turned evil. Meanwhile, Maria tells Sarah that the Slitheen have Luke. They go upstairs to talk to Mr Smith and find out that he's turned on them as Alan appears. They are nearly killed as Mr Smith fires bolts of energy from a built-in gun.

The Slitheen take Luke to the Pharos Institute, where they test his abilities. Luke overcomes the Slitheen and escapes as Maria, Alan and Sarah arrive. Working together, Sarah's gang and the Slitheen discover Mr Smith's intentions. Alan adapts a computer virus to destroy Mr Smith. Using the Slitheen teleporter, Sarah arrives in her attic, where Mr Smith is using Luke to awaken other Xylok from the Earth's core. He plans to crash the Moon into the planet, cracking it open like an egg and freeing the other Xylok. Clyde returns when Mr Smith states he is merciful, but Mr Smith then threatens the humans with its gun. Sarah unlocks a safe and calls on K9 Mark IV. The robots battle and Sarah inputs the virus, which makes Mr Smith forget its purpose. As the Moon grows closer to the Earth, Sarah tells Mr Smith it has a new purpose: to safeguard planet Earth.

The Moon returns to its original position, K9 goes back to the safe to guard the black hole and the Slitheen return to Raxacoricofallapatorius. As Sarah, Maria, Luke, Clyde, Alan and Chrissie watch the ship leave, Sarah reflects that she never thought she could be part of a family.

Cast Edit

Crew Edit

General production staff

Script department

Camera and lighting department

Art department

Costume department

Make-up and prosthetics


General post-production staff

Special and visual effects


Not every person who worked on this adventure was credited. The absence of a credit for a position doesn't necessarily mean the job wasn't required. The information above is based solely on observations of the actual end credits of the episodes as broadcast, and does not relay information from IMDB or other sources.

K9's creator credit in part 2 only.

References Edit

Individuals Edit

Locations Edit

Organisations Edit

  • Alan mentions the FBI.

Objects Edit

Species Edit

Cultural references to the real world Edit

Other Edit

Story notes Edit

  • This episode ends with Sarah narrating. This closes the first series, just as a narration by her opened the series in Invasion of the Bane. This carried on throughout the remaining four series.
  • Both episodes were aired on the CBBC channel, and were broadcast a week later on BBC 1.
  • When the inspector questions Sarah, a page of her confidential UNIT file is visible on screen. The text is taken from the BBC's UNIT website and includes the in-joke that UNIT's activities span "the sixties, the seventies and some would say the eighties". This is the first on-screen reference in SJA (and indeed the entire Doctor Who TV franchise) to the UNIT dating controversy. It was followed by a similar in-joke spoken by the Tenth Doctor, as he reminisced about working for UNIT in the '70s, "or was it the 80s?" (TV: The Sontaran Stratagem)
  • This episode marks the last televised major appearance of the Slitheen. They were featured in both The Gift and The Nightmare Man, but these were both minor appearances. They have however since appeared in other mediums as the main antagonists.
  • Mr Smith nearly caused the catastrophe that the Silurians feared: the moon crashing into the Earth.
  • Clyde was originally going to confront the embodiment of Mr. Smith in the void.[1]

Ratings Edit

  • Part 1 - 465,000 (CBBC)
  • Part 2- 659,000 (CBBC)

Filming locations Edit

to be added

Production errors Edit

If you'd like to talk about narrative problems with this story — like plot holes and things that seem to contradict other stories — please go to this episode's discontinuity discussion.
  • At one point, it says "21" on Sarah Jane's door, which is the real-life number of the house that is used for Sarah Jane's house.
  • When Nathan reveals himself to Luke as Carl and unzips his body suit, the Slitheen next to him can be seen without their heads on.
  • At another point, when the moon is crashing down onto Earth, the moon can clearly be seen over lapping the building outside the window.
  • At 25:58 on Part 1, Clyde, as he opens Sarah's door, looks behind him and looks to the camera until he closes the door.

Continuity Edit

Home video releases Edit

External links Edit

Footnotes Edit

Community content is available under CC-BY-SA unless otherwise noted.

Fandom may earn an affiliate commission on sales made from links on this page.

Stream the best stories.

Fandom may earn an affiliate commission on sales made from links on this page.

Get Disney+