First Epistle of Clement.
The Wikipedia summarises the book thus:
"The story revolves around Judith, a daring and beautiful widow, who is upset with her Jewish countrymen for not trusting God to deliver them from their foreign conquerors. She goes with her loyal maid to the camp of the enemy general, Holofernes, with whom she slowly ingratiates herself, promising him information on the Israelites. Gaining his trust, she is allowed access to his tent one night as he lies in a drunken stupor. She decapitates him, then takes his head back to her fearful countrymen. The Assyrians, having lost their leader, disperse, and Israel is saved. Though she is courted by many, she remains unmarried for the rest of her life."
For Catholics, Judith can be seen as a type of Our Lady, hence the Magnificat antiphon for Saturday (I Vespers of Sunday) this week says:
" O Adonai, Lord God, great and wonderful, who didst give salvation by the hand of a woman: hear the prayers of Thy servants."