Fan Casting Doctor Who The Return of the valeyard (1991)

The Doctor took Katie and Henrick to see the Interstitial Mass Transit System in the 22nd Century. While there, the Doctor and Katie met Kadiatu Lethbridge-Stewart whilst combatting an entity the Doctor nicknamed Fred which was attempting to enter their universe using the Sol Transit System. After Fred had fully possessed Henrick, the Doctor, Katie and Kadiatu followed him through a portal. It was only later that the Doctor learned that Katie had died, after the tunnel they were in collapsed, sucking her out into the vacuum of space.