This chapter examines the resurgence of suspicions among republicans towards real or imagined loyalists in the three counties, that some Protestants were acting as a loyalist ’fifth column’ for the security forces and/or paramilitaries in Northern Ireland. A successful loyalist cross-border paramilitary campaign in the early 1970s precipitated an IRA counter-intelligence operation to eliminate spies in the three counties. Families that were well known locally for their historical involvement in loyalism were again targeted by the IRA in the 1970s. The chapter outlines the suspicions and inter-communal violence in County Monaghan that led to the murder of Senator Billy Fox and the burning of the family home of his fiancée, Marjorie Coulson.