In the three skeleton key how does it foreshadow the danger the lighthouse keepers will face from the title?

Three Dog Nightmare' by Chuck Negron (lead singer for the 3 dog night).. oh man, what a great book! Here's a salpme: I shoved drugs into my system like a little kid eating candy. And in the end, it took away everything: my money, my fame, my wives, my children, and my self-respect. I traded a Mediterranean-style villa in the Hollywood Hills for a corner of an abandoned building where I slept on a filthy mattress I found in a vacant lot.