From the Richmond Dispatch, 3/9/1863, p. 1, c. 6
Attempted Escape. – Capt. A. C. Webster, now confined in Castle Thunder, charged with the murder of Capt. Simpson, a Confederate officer, made on Saturday night, a second attempt to get out of prison. For this purpose he procured an old file and relieved himself of his leg irons and hand cuffs. He and a confederate were to sally out and kill the sentinel, and trust to luck. The plan was discovered and frustrated.