The team initially forgets it is his birthday, adding to his feeling of isolation.

Caleb recreates famous Zodiac crimes to lure Harvey back into their childhood "game" of solving ciphers and playing "detective".

Much like the real Zodiac, Caleb sends complex codes to the police. Reid eventually breaks these by realizing they are personal messages to Harvey rather than general threats.

Caleb Rossmore, a former child prodigy and trash collector.

Reid and Prentiss attend a lecture by crime novelist Patricia Cornwell (playing herself), which prompts Reid to reflect on his career path. 🧩 Key Symbols & Ciphers

The episode is heavy on intellectual puzzles and historical references.