Missed few episode help please

What actually happened to lekshmi? Why did Subbu blame Bhalla family for her death? Whose is responsible for her death? How did Bhalla family find the truth?

So basically...Subbu, Lakshmi and their son was living in London..Raman's cousin Neha was in love with Subbu and wanted him and blah blah..she lied to Shaila bua(who is her mother) that they were having an affair and that she was pregnant with Subbu;s child. when toshi went to London(remember during Mani track) then she found out and went and told Lakshmi abut it..she was pretty mean about it.. she didn't know that it was Ishita's ex subbu..so Lakshmi took it to heart, took Karthik with her and jumped from the building in front of Subbu so for that he is avenging the Bhalla parivaar.