Concern where it was odd to be given. Nothing more.
[ It's more of an answer than Garrus probably expects, but it's also clear why Sebastian is willing to give it. It doesn't exactly say much about what it was that made Sebastian suspicious nor who it came from. In fact, from anyone else, it would sound particularly paranoid, but with Sebastian's personality, he at least gives the impression that he wouldn't speak of it at all unless he was more certain. ]
no subject
[ It's more of an answer than Garrus probably expects, but it's also clear why Sebastian is willing to give it. It doesn't exactly say much about what it was that made Sebastian suspicious nor who it came from. In fact, from anyone else, it would sound particularly paranoid, but with Sebastian's personality, he at least gives the impression that he wouldn't speak of it at all unless he was more certain. ]