The phrase "convoluted plot" means a story or situation that is very complicated, filled with unexpected twists and turns, making it difficult to follow or understand. Full definition
The movie is fun, but it suffers from an overly convoluted plot, under utilization of popular characters, and the addition of too many unnecessary characters. (fatmovieguy.com)
Poor editing, terrible character development and a rather convoluted plot all work against it. (digitalshortbread.com)
The movie has a fairly convoluted plot, involving who is sleeping with whom, and why, and who finds out about it, and what happens then. (rogerebert.com)