In the opening scene of A Christmas Code, Lady Gwyneth Beaumont is performing the quadrille, a lively dance performed by four couples in a rectangular formation. The dance first became prevalent in France in the mid-1700s and was introduced to English society shortly after the turn of the century. It became popular in the upper classes about 1816. Many dance historians claim the quadrille was the precursor to the contemporary style know as square dancing.
You can see this energetic and popular dance performed here: https://www.youtube.com/watch?v=VSD37PF2_Dw
A Christmas Code is available for just 99 cents at online retailers through the holiday season.