The psychotherapist working with Doc and Louisa has suggested a bit of homework...for Louisa to plan an activity start to finish and the Doctor to simply go along with whatever she plans. This is because in their relationship, she is mostly passive and he's quite controlling...and so Louisa plans a picnic.
At the same time, the Doc is struggling with that darned dog--it keeps showing up and following him about* at work and home. He is about to euthanize it** when Louisa stops him and demands he find a home. So, he takes it to a completely idiotic holistic vet. Why she's an idiot, you learn through the course of the show.
Additional topics covered is the pathetic Penhale planning on a picnic to get closer to a lady, Mr. Large operating a still and an obnoxious girl who seems to have some sort of seizure disorder. None of the topics in and of themselves are very interesting and a rare flat episode overall.
*Through the course of the series, a variety of scruffy dogs are used. You wouldn't normally notice this unless you are binge- watching.
**I really thought having Martin trying to kill the dog was a BAD decision by the writer. While Doc is a jerk, he never seemed so cruel as he is here. Bad decision.