British intelligence had infiltrated the United Irishmen and managed to arrest most of their leaders on the eve of the rebellion. Though not among those taken at the house of Oliver Bond on 12 March 1798 (see Lord Edward Fitzgerald), he was arrested about the same time, and was one of the leaders imprisoned initially at Kilmainham Jail and later in Scotland at Fort George until 1802. Upon his release he went to Brussels where he was visited by his brother Robert Emmet in October 1802 and was informed of the preparations for a fresh rising in Ireland in conjunction with French aid. However, at that stage France and Britain were briefly at peace, and the Emmets' pleas for help were turned down by Napoleon.