The ghost (really an alien) was destroyed after making a terrible mistake. Several billion years later, it realised that Cambridge University presented a unique opportunity, featuring both an individual that it could communicate with (Coleridge) and an individual with access to a time machine (Reg). Frustratingly for the ghost, Coleridge was only able to be influenced when he was deeply *relaxed* after consuming heroic amounts of laudanum, and hence unable to be a truly useful conduit for its desires.

> “I tried to tell him my story,” admitted the ghost, “I—”  
“Sorry,” said Dirk, “you’ll have to excuse me—I’ve never cross—examined a four-billion-year-old ghost before. Are we talking Samuel Taylor here? Are you saying you told your story to Samuel Taylor Coleridge?”  
“I was able to enter his mind at… certain times. When he was in an impressionable state.”  
“You mean when he was on laudanum?” said Richard.  
“That is correct. He was more relaxed then.”  
“I’ll say,” snorted Reg, “I sometimes encountered him when he was quite astoundingly relaxed. Look, I’ll make some coffee.”  
He disappeared into the kitchen, where he could be heard laughing to himself.
“It’s another world,” muttered Richard to himself, sitting down and shaking his head.   
“But unfortunately when he was fully in possession of himself I, so to speak, was not,” said the ghost, “and so that failed. And what he wrote was very garbled.”

In an attempt to make Coleridge more amenable to helping (possibly to gain sympathy?) the ghost evidently recounted its story, which Coleridge later turned into a poem. On several occasions, the ghost was able to gain sufficient control over Coleridge to actually get him to speak to Reg, but it was again frustrated to find that very thing that made him receptive (the laudanum) prevented him from making any sort of *useful contact* with the Professor.

> “Professor,” called out Dirk, “this may sound absurd. Did—Coleridge ever try to… er… use your time machine? Feel free to discuss the question in any way which appeals to you.”  
“Well, do you know,” said Reg, looking round the door, **“he did come in prying around on one occasion, but I think he was in a great deal too relaxed a state to do anything.”**

Spin forward two hundred years and **the ghost's story (as related in the poetry of Coleridge) was successful in influencing Michael Wenton-Weakes to become the perfect conduit for its will.**

> The words were very familiar to him, and yet as he read on through
> them they awoke in him strange sensations and fearful memories that he
> knew were not his. There reared up inside him a sense of loss and
> desolation of terrifying intensity which, while he knew it was not his
> own, resonated so perfectly now with his own aggrievements that he
> could not but surrender to it absolutely.

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When Dirk changes the poem (by [distracting Coleridge][1]) the ultimate effect is to **prevent Michael from being influenced, and hence leaving the ghost impotent to travel back in time and prevent its ship from exploding.**


  [1]: https://en.wikipedia.org/wiki/Person_from_Porlock