There are two ways this can start:
1) Usman Abdullah's lift accident was purely accidental (if their bungalow can set on fire their lift can break as well).
2) Mir Khan or someone else related to Usman Abdullah's "darkside" plotted the elevator fall, but roundabout the blame will go to Zubair (his mysterious disappearance might instigate it).
The way Zubair said koi zaroori kam had a sort of genuineness to it, so Zubair is Paapi, but the way the child rejected that paapi wasn't her "paapa" kind of hints at the fact that he might not be their father. Maybe Zubair had a sister who past away whose children Zubair takes care of or maybe they are some adopted kids who Zubair takes care of (he most likely isn't married based on his and Aliya's conversation about "Nats" unless he is married to "Nats" which is why he was so confident that his mother would accept her in which case the kids would be his).
Aliya also won't get the blame for what happened directly or indirectly (based on Surraiya reading the text message), because both Rizwan and Ayaat are fully informed about the office plans and have been up to date with all the planning since the start and either of their words can easily dispel any misunderstanding.
Comment on what you think about my predictions/views. Agree/disagree?