The contract
Everything in this series runs off a single document signed in the second episode. If you are confused later, it is almost always because you missed a clause.
The secret
Handled with more patience than the genre usually allows. The reveal is placed after you have already decided how you feel about both people, which is the point.
The ending
Read the final scene as an answer to the first one. The series is a closed loop, and it rewards a rewatch more than almost anything else on the shelf.
