Ellie Walker makes her first appearance as Mayberry's first female pharmacist. Whe she agrees to take over the day to day duty's of Walker's Drugs for her uncle Fred she quickly finds herself at odds with most of Fred's customers. Mayberry's laid back and trusting style at first does not suit Ellie and she ends up making enemies faster than she makes friends.
Things really get nasty when Ellie refuses to sell Emma Watson her "pills" because she does not have a prescription. Emma's health goes downhill fast and Ellie finds herself quickly becoming the town villain, being blamed for Emma's declining health. Andy tries and fails to resolve the situation.
In the end, Ellie begins to see Andy's way of thinking, that perhaps it's more important to consider the needs of the people you live with than it is to follow rules and regulations, even if you swore to follow them.
It turns out Emma's "pills" were not medicinal at all, that her condition was all in her head, so she was never in any real danger.