After taking the waterbus over from Penarth, Alice heads along the route from docks that eventually leads into Mermaid Quay. Considering that Torchwood is right there, she wouldn't be surprised if she saw an alien nearby or one of the three team members, or some sort of Rift activity, whatever it might look like.
What she would be and very much is surprised by is a young blonde woman suddenly tumbling out of nowhere and into what looks like a very painful landing. Alice doesn't know what's going on, but she runs over to the woman, already pulling her mobile out in case she needs to call for medical. Or Torchwood.