The Algebra of Ice

Edgar Allen Poe lies dying in a gutter in Baltimore... The Doctor and Ace cannot help him - his death has already happened. Poe will be taken to a hospital, and will die in three days time without ever coming out of his coma. But even as the Doctor explains this, the man in the gutter groans and expires. Bewildered, the Doctor hurries Ace back to the TARDIS. At the door, they look back and see that the gutter is empty. In a moment, Poe staggers around the corner, drops to his knees in the gutter, then gets up and stumbles into another bar... Can the Doctor discover what is causing the time anomaly? Will he be able to prevent the universe itself from unraveling when everyone seems to have turned against him - even the TARDIS? Will he be able to escape the cold hell of absolute order? The answer, it seems, lies in the algebra of ice...