How to Design classes in OOPS way to respond to search query with complex filter

We have search query with Complex search criteria. To serve this request, lot of data(modeled as multiple in memory POCOs , some data gathered from External Rest Services, Some data queried from DB) need to be queried and then business logic needs to be applied on top of this data. Current solution uses Manager class to gather data from all these sources and feeds it to Domain Model :that has methods to act upon data and perform filter operations. But Manager class method is having around quite lot of code to get data from multiple sources (around 15 calls ) and then set the data in Domain model and then call Domain model methods to act upon it. This makes it look dirty and procedural. Can anyone suggest more cleaner approach/ pattern to use.