"This is where it all begins," Kovarian hissed as she bent to leer at the monitor in an almost serpentine fashion. She watched the Astronaut emerge robotically from the lake and approach the Doctor. She was practically salivating at his imminent death, her hand poised over the control that would fire the killing charges when she heard a voice behind her. "I'm afraid you're very wrong."
Kovarian pivoted on her foot and and gaped as she came face to face with her destined warrior, her perfect tool - River Song. River's eyes were cold and merciless, and in her right hand was an alpha-meson pistol pointed straight between Kovarian's eyes. "You see, Madame Kovarian, this isn't where it all begins. This is where it all ends." Kovarian's eyes narrowed and she barked a short, bitter laugh. "You perfect fool. You forget we made you, we trained you. You are what you are today because of us. You won't pull that trigger. To do so would allow your poor, stupid parents to retrieve you from that suit and irrevocably change your timestream and the timestream of that so called beautiful idiot. We ingrained that into you, Melody Pond. Ironic, isn't it? The very instruments of the Doctors' death have more respect for time than he ever did." Kovarian lifted her chin a little, her air of smugness returning by degrees. "You don't have the courage."
River's smile was an awful thing to see and chilled the blood in Kovarian's veins to rivulets of ice. "You're very wrong, Madame. Because, you see, you made one fatal error. " She paused, finger beginning to tighten on the trigger. "You're assuming I'm your Melody Pond. All your machinations, all your schemes, and it never occurred to you the mistake you made in bragging to my beloved about fooling him twice in the same way? You tipped your hand far, far too early. You gave him time to think - to plan. So now, before my child self can make the mistake of her lifetime.."
Her finger tightened on the trigger and a neat hole appeared on Kovarian's forehead. Kovarian let out a soft whimper and fell dead to the floor. Temporal winds began to stir as River ran to the window and pressed her face to the glass in time to see her younger self open her faceplate. The winds became stronger and stronger as River whispered what she knew she was saying down below. "Help me.."
Kovarian's body disappeared even as the windows exploded outward. River flung her arms wide and activated her vortex manipulator, a triumphant smile gracing her beautiful features.
The Doctor took the astronaut's gloved hand in his own. "Come with me, Melody Pond. It's time to go home now."