In July 1864, Confederate General Jubal Early launches a surprise raid that takes him to the very gates of Washington DC. The city is in panic. Almost every able-bodied soldier from the Union has already been sent south for the siege of Petersburg, more than 100 miles away. The only defenders remaining are clerks, government officials, and the Invalid Corps. Made up of men injured in battle or by disease, these "hopeless cripples" must hold out for a desperate 24 hours until Union General Grant can send reinforcements. With Lincoln himself on the ramparts, they cannot afford to fail.