Viewers were really confused by the twist in Strike: The Cuckoo's Calling
Spoilers for the last episode of the BBC1 JK Rowling adaptation

Last night saw JK Rowling’s grumpy private investigator Cormoran Strike solve his first case on TV, in BBC drama adaptation Strike: The Cuckoo’s Calling.
But the murderer wasn’t who many viewers suspected. The man Tom Burke’s character revealed was the killer of Lula Landry (Elarica Johnson) was... her adoptive brother John (Leo Bill).
However, the twist left viewers with an entirely new mystery: if John killed his sister, why on earth did he hire Strike to investigate her death in the first place?
https://twitter.com/fatanklesjules/status/904464494012891136
https://twitter.com/GHulkes/status/904455902547333125
https://twitter.com/cjmckeon/status/904448873397149696
https://twitter.com/da_walkingdead/status/904447079925387266
https://twitter.com/Josephburne/status/904446566114758656
https://twitter.com/GSWooster/status/904461106336411648
Don’t worry though, Strikers, as we’ve fully explained here, there was a reason for John’s actions.
In JK Rowling’s original novel, John hires Strike in order to frame Jonah Agyeman (Lula’s biological half-brother, played by Abubakar Salim), in an effort to conceal the fact that Jonah stood to inherit Lula’s fortune in the event of her death. So, although the motive wasn't fully explained in the BBC show, it all came down to money.
But don’t worry if that episode confused you – last night the BBC was asking viewers who killed ‘Lulu’...
https://twitter.com/BBCOne/status/903920467588792321
https://twitter.com/jk_rowling/status/904403799158267904
This isn't the last we've seen of Strike though – he's back this weekend for a new mystery (in which, again, nobody kills Lulu).