Sentinel fic on Earth

I've been searching for a Sentinel/SGA crossover but all I can remember is the end.  It takes place on Earth and I think both boys are detectives.  At the end Elizabeth asks where their 'area' is (the idea being that sentinels and guides cover a particular town/city/state) and they grin and reply Earth.

Does anyone recognise this please?

Thank you

Daisy May

FOUND by endof_thyme  'Signs' by flitterflutterfly  http://archiveofourown.org/works/692734