Patient zero recovered from a Rift a month ago by a MI5 unit. She's considered highly dangerous and should be executed with extreme prejudice.
Arriving at Calais, France they took a small boat to ambush the transport carrying the target. After the first engagement, where Karina used her ice powers the agents managed to eliminate the girl. Katerina was killed and as Isabella was about to die she tried to defect and offered to help however she could. As such Karina radioed Alaric and he rewound time about 10 minutes, hoping that their defector could sabotage the mission.
On the second attempt, things went even worse as the MI5 agents got killed quicker as the KGB agents chased them into the city, avoid the coast guard. Isabella's subtler sabotaging attempts failed as eventually Katerina managed to catch up with the DGSI car. In the firefight ms. Bauer ran away, while agent Kotov stayed determined and managed to kill Elaine Benson before reinforcements arrived capturing her and handing her over to the DGSI agents to interrogate her and hopefully gain some information out of her.
Alexandra had one last conversation, as Katerina declared that she did everything for the greater good and that she is loyal to the Union. Meanwhile Isabella made her way back to Berlin where Alaric approached her and she agreed to kill agent Petrov. After recovering and meeting with the man, she gunned him down in front of the local Belmont before agreeing to work with Alaric, as he inducted her into the Stone transporting her to New York.