A Face from the Past: Sir Thomas needs an heir. But he's impotent. What must his wife do?

When Margaret meets Sir Geoffrey de Grandcourt, her twin brother's best friend, she is smitten and enjoys some intimacy with him. But their plans for the future are destroyed by an unexpected chain of events, and she is married off to an older man - a heroic crusader, Sir Thomas Swanbourne. But Sir Thomas is cruelly injured in a skirmish during a mission for the king, and is unable to create a much-needed heir to continue his line and maintain the family estate. Margaret's ravenous sexual appetite remains unsatisfied, but what can she do? Can anyone provide a solution that might keep everyone happy?