I've cheated and Googled it - there are seven Joshua, Judges, Jeremiah, Joel, Judith, Joel, Job, Jonah - but Judith isn't in the Protestant Bible (and why not? Sexism! Though Esther managed to get in there, good on yer, Esther)
Judith was a beautiful Hebrew widow, in a town called Bethulia, which was under seige by Holofernes, a General of Nebuchadnezzar. Holofernes's advance stopped the water supply and the town almost surrendered. The people lost heart and encouraged their rulers to give way and the leaders vowed to surrender if no help arrived within five days
Judith entered Holofernes's camp at night accompanied only by her maid, went to Holofernes tent and sweet-talked him, plying him with food and drink and promises until he fell into a drunken sleep. Then she beheaded him and returned to Bethulia with the severed head. The Hebrews took heart and defeated the leaderless enemy.
A resourceful woman. She deserves to be better remembered.