Doctor Who: K9 Tales: The Invisible Enemy & K9 And Company

The Invisible Enemy: The TARDIS is infiltrated by the Swarm - a space-borne intelligence that wishes to spread itself across the universe - and the Doctor is infected by its nucleus. The ship then materialises on Titan, one of the moons of Saturn, where the human occupants of a refuelling station have also been taken over. This Doctor Who adventure was the first to feature K9.

K9 And Company: Sarah Jane Smith pays a Christmas visit to her Aunt Lavinia's house in the village of Moreton Harwood. She discovers that Lavinia, a noted scientist, has yet to return from a lecture tour of the USA. She does however meet Brendan - Lavinia's ward - and Commander Bill Pollock - her partner in a small market garden business. Also in the house, in a box sent to her by the Doctor, she finds K9. Brendan is kidnapped by a local coven of witches who want to sacrifice him to the goddess Hecate. Sarah, with K9's assistance, sets out to try and foil their plan.