Pimpernel was one of the rabbits to escape from the Sandleford Warren destruction with Holly, Bluebell, and Toadflax as it was being destroyed by men. Bluebell discovered him during his own escape down a little used run that led into the forest and described him as being in a bad way, gasping from exposure to the poison that the men used to kill the rabbits. Once outside, he and Bluebell found Holly and Toadflax and they made their way through the forest, following Holly's plan to find Bigwig and tell him that he had been right. During the beginning of the journey, Pimpernel was described as light headed, talking nonsense and feverish and we assume that he has been affected a great deal by the poison.
Once they reached Cowslip's warren and asked the rabbits there for Fiver, Bigwig, and Hazel, they were attacked. Pimpernel, too ill and outnumbered, was killed in the attack.
TV series
In the television series, Pimpernel chose to stay behind at Cowslip's Warren while Holly went on to look for Bigwig and the other Watership rabbits after escaping the destruction of Sandleford Warren. Sometime afterwards, Pimpernel ended up in a snare, and the rabbits of the Warren of the Shining Wires never spoke of him to Holly, Hazel, Bigwig, and Fiver until they later learned of Pimpernel's fate and the dark side of Cowslip's warren.