Four conspirators were killed at Holbeche House: Robert Catesby, Thomas Percy, John Wright and Christopher Wright.
After the Gunpowder Plot failed, the fugitives raided supplies and took shelter at Holbeche House in Staffordshire on 7 November 1605. Their gunpowder had become damp in the rain, so they spread it near a fire to dry. A stray spark ignited it, badly injuring several men, including John Grant and Ambrose Rookwood.
The following day, 8 November, Sheriff Richard Walsh and his men surrounded the house. In the resulting exchange of gunfire, John and Christopher Wright were shot, while Catesby and Percy were reportedly struck by the same bullet. The four later died from their wounds. Thomas Bates and others escaped or were captured rather than killed there.
A common mix-up is to count the men injured by the accidental explosion. That incident involved several conspirators, but the four counted in this question are those killed during the confrontation at Holbeche House.