Character mistake: When Laura says that Alyssa was probably only sleeping with the doctor so he wouldn't be able to testify against her, the doctor says "She's my patient, nothing more." But she isn't his patient, her husband is.
Other mistake: When the girls see Dan in hospital, his IV is dripping, but in another shot we can see that the wheel on the IV that controls how fast the IV is dripping is turned off; it's right at the bottom, so it can't be dripping.
Continuity mistake: The first time we see the land rover, Rosemary's hair is flat, with the window closed; then, suddenly, her hair is being blown around, as if the window is open to accommodate a camera.
Except for the first episode, "And No Birds Sing", where Laura drinks a glass of wine in 2 gulps, she never takes a sip of her drinks - wine, apple juice, nothing - except for tea. She pretends to drink, but doesn't succeed.