Craddock was the medic for the town of Moslin on the planet of Atharna.
He was the indirect reason for the death of Katherine Steele's partner, who died when Craddock tended to a criminal before them. As a result, Katherine held a grudge against Craddock.
Craddock later tended to Felicity and Brian after they crashed into the planet once the Eighth Doctor helped them there. Upon finding out the truth behind Brian, he, along with Katherine, Samson and the Doctor, decided to help save Felicity and Sophie Russell from Brian. But when Craddock charged at Brian, he was killed. (AUDIO: He Kills Me, He Kills Me Not)