How to get record id when use RetrieveMultiple plugin

Hi all,

I have to create a subgrid in Account Form to show all CampaignResponse  in the subgrid. But an account record maybe have multiple child accounts. An account maybe have multiple contacts. I created a contact field in CampaignResponse entity to make relationship between Contact & CampaignResponse. I created a RetrieveMultiple plugin to update query for the subgrid but I can't get account record id in the plugin to get all CampaignResponse which related to Contact. 

Anyone can help me to resolve this issue?

Thanks