Four New York prison guards have been charged with stealing a Salvador Dali sketch from the city's main jail and replacing it with a copy.
Dali drew the picture to apologise for missing a lesson
The four Riker's Island guards were charged on Tuesday with taking the artwork during an unscheduled fire drill.
The prosecution says the men believed they could sell it for $1million.
All four have pleaded innocent to grand larceny.
A lawyer for one of the men says an audio tape that is a key part of the prosecution case does not prove the guards' guilt.
The men have been named as Benny Nuzzo, 49, and Mitchell Hochhauser, 40 - whom the prosecution believes were the ringleaders - and Timothy Pina, 44, and Greg Sokol, 38, who were stationed near the sketch.
They have all been suspended without pay. If convicted, they face a maximum of 15 years in prison.
Dali drew the picture by way of an apology for missing an art lesson he was supposed to give at the prison in 1965.
Moved for safety
The drawing, a surrealist image of Jesus being crucified, hung in the prison cafeteria for years before being moved to a lobby where officials thought it would be safer.
Riker's Island's roughly 15,000 prisoners do not have access to the lobby, which is used only by prison personnel.
"Who knew that it might have been safer left in the cafeteria?" a spokesman for New York Mayor Michael Bloomberg asked.
In a vanishing act echoing the film The Thomas Crown Affair, the picture was stolen in March from its usual position and replaced with a replica - despite a 24-hour guard in the lobby.
The original, last valued at $175,000 back in 1985, is believed to have at least tripled in value since Dali died in 1989.
According to the New York Post, one of the prison's officers noticed that the image in the locked display case where the picture was housed "didn't look right".
Several more officers examined the picture and, having drawn the conclusion that something was amiss, called the police.
Dali drew the sketch as an apology to Anna Moscowitz Kross, then the Corrections Commissioner, after he was unable to attend a talk on art for the prisoners at Riker's because he was sick.
He dashed out the picture in just two hours and despatched a friend to deliver it.
On the corner he had written "For the dinning room of the Prisoners Rikers Ysland [sic] - SD".
And there it hung for 16 years until it was re-housed in the jail's lobby.