What is the source of the allusion in the sentence below?
Reopening the investigation would be like opening Pandora's box.

 - a song
 - Greek mythology
The source of the allusion Pandora's box is Greek mythology.
In Greek mythology, the gods send Pandora a box and instruct her never to open it. Curiosity overcomes Pandora and she opens it, unleashing evil into the world.
The allusion Pandora's box means a source of many problems.