Global Search from external site (Portal Hub) --> send user with results to HTML5 viewer.

I want to have a Global Search execute from an external website's (my portal hub site) textbox.  Any thoughts on how I might configure this?  The goal is to allow a user to search from my portal hub, and have them taken to my HTML5 viewer with the found results.  I would like to use Workflow 5 to do this, but I'm not sure where to start.  I think I'd need to do an Essentials site REST search, pass the resulting feature set into a workflow that reads the feature set and opens the viewer with the results.