Restoration historiography has so far remained silent regarding the alliance between the exiled royalists and the recusant religious houses in the Low Countries. This article examines the assistance provided to the royalist cause by Abbess Mary Knatchbull of the English Benedictine cloister at Ghent. The correspondence of Charles's leading advisers, most notably Sir Edward Hyde, reveals the extent to which the conspirators relied upon the nuns' mail service to communicate with their supporters in England and abroad, and upon the abbess's ability to obtain funds from local financiers. While the nuns were not central players in the conspiracies of the late 1650s, their activities reveal the royalists' dependency upon the networks established by Catholic exiles. The article also explores Mary Knatchbull's motives for devoting so much of her community's temporal and spiritual resources to the royalist cause. The rewards she sought from the king after 1660 suggest that she had a definite religious and political agenda which aimed ultimately at Catholic toleration. Therefore the article raises several important issues about Charles II's and his ministers' links with English Catholics and, in particular, it points to the important role of women in the hitherto masculine territory of royalist conspiracy and politics.