Complex sentence: On studying some drawings by Mukul that represent scenes from the past, Dr. Hajra concludes that Mukul's drawings as well as his desciptions are of events around a fortress, where the boy's father (sic) had worked as a gem cutter.
Split into simpler sentences: On studying some drawings by Mukul that represent scenes from the past, Dr. Hajra concludes that the drawings of the child Mukul represent scenes from a former life. It emerges that everything had taken place in a fortress, where the boy's father had worked as a gem cutter.