The Knave of Hearts is mentioned first in chapter 8, and chapters 11 and 12 deal with his trial for a tart robbery in which the King of Hearts presides as judge. Alice eventually defends the Knave after the evidence becomes increasingly absurd and she is called as a witness.
The White Rabbit announces the charges as:
The Queen of Hearts, she made some tarts,
- All on a summer day:
The Knave of Hearts, he stole those tarts,
- And took them quite away!
The Knave rarely speaks during the trial. The Mad Hatter is called to give evidence but spends his entire time being nervous in front of the King and Queen of Hearts, and the Duchess's cook is summoned to tell the court what tarts are made of. Neither is a convincing witness, and the Knave does not offer a very good defense. He denies he wrote a letter that mysteriously appears in the court, but that he already knows isn't signed.
Fortunately for him, Alice diverts the attention of the court by growing ever and ever larger and arguing more and more, lastly with the Queen over the concept of "sentence first—verdict afterwards". Before a verdict can be reached for the Knave's innocence or guilt, Alice reaches full size and forcefulness, and then calls them "nothing but a pack of cards". They attack her, ending the trial.
It is believed by some people  that since Sir John Tenniel's illustration of the scene in chapter 12 has the Knave with small club outline shapes on his blouse, the ultimate nonsense is that the King and the Queen do not even have the correct person standing trial, this isn't the Knave of Hearts at all, and whoever it is unwilling to clarify the matter. However, this would also suppose Alice, the White Rabbit, the Mad Hatter and everyone else missed it as well, and that Carroll inserted an unintroduced character. After calling him "the Knave of Hearts" twice in chapter 8, the rest of the chapter simply refers to him as "the Knave". The only other non-heart card characters in the book are the three gardeners (drawn as spades), the ten soldiers (described and drawn as clubs), and the ten courtiers (described as diamonds). For other illustrations involving the Knave, the original art by Carroll for chapter 12 and the chapter 8 drawing by both Carroll and Tenniel show no markings.
Crispin Glover played the Knave of Hearts in the Tim Burton film Alice in Wonderland. In the film, the relationship between the Knave and the Queen serves more as the Knave being the Red Queen's personal assassin. However, much like the other servants of the Queen, the Knave hates her though he plays on her insecurites until she is dethroned and attempts to kill her after being forcefully handcuffed to her to accompany her into exile. His real name is given as Ilosovic Stayne. He is also a major villain in the video game adaptation of the film and the second boss.