The TARDIS materialises in Paris in the year 1572 and the Doctor decides to visit the famous apothecary Charles Preslin. Steven, meanwhile, is befriended by a group of Huguenots from the household of the Protestant Admiral de Coligny. Having rescued a young serving girl, Anne Chaplet, from some pursuing guards, the Huguenots gain their first inkling of a heinous plan being hatched at the command of the Catholic Queen Mother, Catherine de Medici.

William Hartnell
as The Doctor / Abbot of Amboise

Peter Purves
as Steven Taylor

David Weston
as Nicholas Muss

Eric Thompson
as Gaston, Viscount de Lerans

Annette Robertson
as Anne Chaplet

John Tillinger
as Simon Duvall

Christopher Tranchell
as Roger Colbert

Erik Chitty
as Charles Preslin

Edwin Finn
as Landlord

Clive Gazes
as Captain of the Guard