The House Across the Lake uses the motif of reflective surfaces, such as the lake and the glass wall, as a symbol for things that seem transparent but have hidden depths, like people and marriages. Throughout the novel, the lake is a recurring image, reflecting the characters’ feelings and actions. The glass wall in the house also serves as a reflection of the characters’ lives, showing the truth behind their facades.

The lake represents a metaphorical barrier between the public and private lives of the characters. It is a physical barrier that separates the two houses, creating a sense of isolation for both Katherine and Casey. It also serves as a reflection of their emotions and secrets, as seen in the changing colors of the lake. The lake appears peaceful and serene, but it has hidden depths, just like the characters’ lives. It is a metaphor for how things may seem clear on the surface, but the truth may be murky and uncertain.

The glass wall in the house also reflects the theme of Marriage and Secrets. It is a barrier between the inside and outside, but it also serves as a mirror, reflecting the truth behind the characters’ lives.