There's nothing wrong with Prisoners of the Lake; it's an enjoyable enough story on its own, but it's a very typical story of the Pertwee Era. Treloar does a relatively good job portraying Pertwee's Doctor; Katy Manning is also good here as Jo Grant, with her loyalty to the Doctor on full display and her bravery and competence. Mike Yates is present as well, and he's well-written and well-played.