"The Adventure of the Cardboard Box" is one of the 56 short Sherlock Holmes stories written by Sir Arthur Conan Doyle.

Miss Susan Cushing of Croydon receives a parcel in the post that contains two severed human ears packed in coarse salt.

Inspector Lestrade of Scotland Yard suspects a prank by three medical students whom Miss Cushing was forced to evict because of their unruly behaviour.

He reasons that a medical student with access to a dissection laboratory would likely use something other than plain salt to preserve human remains, and would be able to make a more precise cut than the roughly hacked ears suggest.

The address on the package, roughly written and with a spelling correction, suggests to Holmes that the sender lacks education and is unfamiliar with Croydon.

In the end, her husband's inability to accept her betrayal, and sheer jealousy at discovering the affair, causes him to commit what Holmes considers a "crime of passion".

(The text of the moved passage runs from "Our blinds were half-drawn, and Holmes lay curled upon the sofa" to "I should not have intruded it upon your attention had you not shown some incredulity the other day.")

The passage seems to have little to do with the mystery but may be a subtle reference to the theme of adultery as Beecher was famously put on trial for the offense in 1875, an event many contemporary readers would have remembered.

The story was adapted for the BBC Light Programme in 1960 by Michael Hardwick, as part of the 1952–1969 radio series starring Carleton Hobbs as Holmes and Norman Shelley as Watson.