The repercussions of their actions.

The Breach is closed, and the toils of the PPDC had come to and end. However, as mass paranoia and fear of another attack are present, our heroes are not allowed to rest yet. (Yes, Raleigh x Mako)

"[S]omething wild churns in him still, a dangerous edge to his moves, a wildness that has found an equal and willing match in her. She will meet him, thrust for thrust." Mako Mori/Raleigh Becket, post-movie. Not very spoiler-y.