In February 1405, the Welsh rebel leader Owain Glyndŵr, Glyndŵr's son-in-law Sir Edmund Mortimer and Henry Percy, 1st Earl of Northumberland, entered into a tripartite indenture that proposed a threefold division of the kingdom. This agreement was apparently connected to a plot to free Mortimer's nephew Edmund Mortimer, 5th Earl of March, from King Henry's custody and carry him into Wales. On 13 February 1405, the young Edmund Mortimer and his brother Roger were abducted from Windsor Castle, but quickly recaptured near Cheltenham. Edward's sister Constance was held responsible and accused her brother of involvement in the failed abduction. He at first denied the charge, but later admitted to knowledge of the conspiracy. He was arrested and imprisoned for 17 weeks at Pevensey Castle, after which he petitioned for release, and by October was gradually being returned to favour. His lands were restored to him on 8 December 1405, and in November 1406, he was again made Constable of the Tower and continued to serve in a military capacity in Wales.