But A Thought is the eighth episode in the fourth Common Series.
"The universe is alive." - Time
The TARDIS has been hijacked, by Malice, one of the Eternal Pantheon, incarnations and goveners of the fundamental parts of the Universe. Malice intends to use the TARDIS to locate the Great Clock, the sigil of his brother, Time. If he destroys the sigil, Time dies and Malice can take his place as both the epitome of time and darkness. The Doctor, Amy and Rory are now caught in the middle of both a race to one of the most powerful objects in the universe and a battle between squabbling siblings, that hold powers beyond comprehension.
- The Doctor - Matt Smith
- Amy Pond - Karen Gillan
- Rory Williams - Arthur Darvill
- Time - Mark Gatiss (voice)
- Biology - Miranda Richardson (voice)
- Spectrum - Terry Jones (voice)
- Force - Roger Allam (voice)
- Ascension - Michael Bell (voice)
- Oblivion - Alan Rickman (voice)
- Malice - Simon Templeman (voice)
- Fawkes - Sam Attwater
- The title of the episode takes its name from a line in Mark Twain's last story, The Mysterious Stranger, which also featured a rather malevolent creature amusing himself by antagonising the protagnists. The line reads: "Life itself is only a vision. A dream. Nothing exists, save empty space and you. And you... are but a thought."