Don’t Judge a Book by the Cover
This person was a nanny for nearly 15 years, so when they say that one family was the worst, it means something. From the outside, the mom and dad seemed as normal as could be, though they did have some pretty strange habits. She worked across the country, and he stayed out until 2 or 3 AM. The mom even went as far as hiring a private investigator to snoop on her husband.
Then the OP found what might have been the source of their seemingly normal mannerisms in public: bottle after bottle of prescription pain killers. Those things can either tear you up from the inside or make you appear as if nothing is wrong with your life.