adoptive son Luke Smith (Tommy Knight), to university. He appears again in series four finale, Goodbye, Sarah Jane Smith. Though he doesn't appear in the serial, it is mentioned in The Man Who Never Was (2011) that Luke invented a special dog whistle to summon him with. Other appearances Literature K9's co-creator Dave Martin wrote a series of four children's books entitled The Adventures of K9, published by Sparrow Books in 1980. K9 is travelling on his own in these stories for reasons not explained. In 1985, a series of gamebooks featuring the Sixth Doctor were published by Severn House under the title Make your own adventure with Doctor Who in Britain and Find Your Fate – Doctor Who in the United States. These books were actually written by scriptwriters for the television series. Martin wrote Search for the Doctor which takes place in the mid-21st century and features Sarah's K9 (at time of publication assumed to be Mark III, but clearly Mark IV in the light of School Reunion) being reunited with the Sixth Doctor long after Sarah's death. A short story, "Moving On", in Virgin Publishing's Decalog 3: Consequences anthology and the Big Finish Productions-produced Sarah Jane Smith audio play Mirror, Signal, Manoeuvre (both written by Peter Anghelides) indicate that K9 Mark III broke down and Sarah was unable to repair it as the replacement circuits would not be invented for several centuries. Another short story, "Tautology", by Glenn Langford (Doctor Who Magazine #194), suggests that K9 Mark III's motherboard will be passed down through Sarah's descendants and eventually end up in the hands of Professor Marius, who will use it to build the first K9, creating an ontological paradox. The Virgin New Adventures seventh Doctor novel Lungbarrow (written by former Doctor TV series writer Marc Platt) featured K9s Marks I and II meeting for the first time on Gallifrey during the events surrounding the disappearance of the Doctor's entire family house and his living relatives, which also featured many previous established Gallifreyan based characters. The two collaborated towards rescuing the Doctor, then current companion Chris Cwej and the Doctor's lost family. This novel also served as the direct lead-in story to the 1996 Doctor Who telemovie. Jealous, Possessive by Paul Magrs, the "Scorpio" story in Big Finish's anthology Short Trips: Zodiac features K9 Mark I and Mark II relaying their exploits to each other, and their veiled