Sam was just seeking a sufficiently private place to relieve himself after getting excessively drunk after work because his wife was working late again. Instead, he witnesses a body being carried out of the Museum, and becomes entirely too interesting to some of the Fae-touched who want to keep him quiet.
Cathy was just trying to remain out of sight of the Fae and her Fae-touched family so she can continue her university studies in Mundanus. Instead she's trapped and brought home by her brother Tom, and informed that she's now betrothed to William.
William has his own ideas, including a preference for Cathy's sister Elizabeth initially, and then for new arrival in Aquae Sulis, Amerlia.