I believe Tom Edge wrote this episode in 3 acts. In part 1 we look at Act 1 and part 2 we look at Act 2.
So, what can we notice about Act 3?
First of all, we are back to referencing the romance between Strike and Robin, which was absent in Act 2.
In scene 23 Pat, Strike’s receptionist, reminds Strike it’s Robin’s birthday. Then, in scene 24 we have a 50 second scene of Strike seeking a shop assistant’s advice over whether to buy Robin a ring. In scene 25 we see he gives her flowers before discussing the case.
Total screen time dedicated to this romance: 2 minutes.
Later, towards the end of this first episode (1 of 4) in scene 34 Strike’s brother arrives and they talk about their father. In scene 35 Strike researches his complex family history on the internet.
Total screen time dedicated to Strike’s personal family background: 4.37. (approx 5 mins).
So, to conclude, Act 3 is a total of approx 27 mins.
Total screen time dedicated to B and C stories: 7 mins (approx 25%) which is exactly the same percentage as Act 1.
Made up of:
2 mins dedicated to romance between the two protagonists (approx 7%)
5 mins dedicated to Strike’s family history (approx 18%).
20 minutes out of 27 are dedicated to solving the case. (approx 75%).