Nicodemus's Book is a manuscript in which Nicodemus, the leader of the Rats of NIMH, recorded the history of their colony and his personal thoughts, plans and worries.

Description and ContentEdit

The Book is a rather thick leather-bound tome adorned with golden metal (that may have been copper). Nicodemus wrote in the book in an ornate script, using Unfading Ink. The two entries whose content is known respectively dealt with Jenner and with Jonathan Brisby, and took up one page each. Their content was as follows:

JENNER has become cold-hearted. He uses his knowledge to fight against the plan of moving to Thorn Valley. I fear other rats may soon be swayed to his opinions. It is wrong to go on stealing.
JONATHAN BRISBY was a mouse of great courage. He made possible the rats' escape from the terrible cruelty of NIMH. He was killed today while drugging the farmer's cat, Dragon.

This was followed by Nicodemus's ornate signature.



The Book was probably crafted by the Rats — possibly by Nicodemus himself. Akin to a sailor's log, it was then used by Nicodemus to record the Rats of NIMH's story. It is believed that its writing was begun shortly after the Rats' arrival on the Fitzgibbon Farm.

Nicodemus's DiaryEdit

The Book was used by Nicodemus to record the Rats' daily history, from their escape from NIMH to the latest events before his death in 1982. This included his thoughts on the death of Jonathan Brisby and his indecision about what to do for his widow, as well as his worries about Jenner's interference with the Plan.

Later FateEdit

As a relic from their original leader, the Rats probably took the Book with them when moving to Thorn Valley; it is assumed that Nicodemus's heir and successor, Justin, used the book to glean some of the late Nicodemus's wisdom from it so that it may guide his own leadership.


The Secret of NIMH (first appearance)
Timmy to the Rescue (flashback)

Differences with the NovelEdit

No such Book is mentioned in the novel.