- Daniel: "Heh... I never thought I'd be getting headshrunk on my own couch by a hot killer ninja."
- Hannah: "Assassins aren't ninjas, dumb-ass. And I've never killed anyone in my life. I work with computers mainly."
- ―Daniel Cross and Hannah Mueller.[src]
Originally working in a tech support capacity for the Assassins, she introduced Daniel Cross to the Assassins after whisking him away from a bar one night when he was experiencing yet another episode of the Bleeding Effect. His hallucinations had led her to mistake him for an Assassin, and for a time, she became his chief companion as he tried to integrate into the Brotherhood's community and learn to cope with his psychiatric issues. She sympathized with him and accompanied him across the globe in his quest to rally the Assassins and locate the elusive Mentor.
Unbeknownst to them, Daniel was a sleeper agent planted by the Templars, set to assassinate the Mentor upon meeting him. Their scheme proved to be a success, and upon committing the deed, the distraught Daniel defected to the Templars for security, divulging the sites of all Assassin cells he had visited throughout his journey and setting off the Great Purge. Ultimately, Hannah herself became a victim of the Purge, murdered by Daniel's own hands as she tried to plea with him.
- "I was born into this."
- ―Hannah about her Assassin affiliations.[src]
Hannah was born into the Order, and trained to become one from an early age. By the latter half of the 20th century, the Assassins reduced their reliance on assassinations to effect change, and thus in Hannah's late 20s, she had yet to kill anyone. This was reinforced by her support role as a computer technician rather than as a field operative.
Finding Daniel Cross
- Daniel: "Where are we? Is this your place? Did we... ?"
- Hannah: "Uhh, no. Gross. No, we brought you here because you were drunk and out of control. And there are some serious questions we need to ask you."
- ―Daniel and Hannah at the camp.[src]
In 1998, during a night out in a Philadelphia bar, Hannah noticed a drunkard muttering strange words and caught him rambling about "Templar". Believing him to be an Assassin too, she followed him and saw Daniel, who was suffering from the Bleeding Effect, pronounce a passerby to be a Templar and ready a knife to kill him. Hannah intervened, reprimanding him for calling attention to himself and ushered him into the backseat of her car. While driving to her Assassin camp, she mistakenly treated him as an Assassin.
The following morning, Hannah woke Daniel after he had fallen asleep in her cabin and told him that they could not find his name listed on any of the Assassin camps, though Daniel had no idea what she was talking about. She took him to meet the camp's director Paul Bellamy, who discovered the Assassin tattoo on his arm.
As the three of them spoke, Daniel abruptly experienced the Bleeding Effect once again and spoke in Russian, the language of the ancestor whose genetic memories he kept reliving. Hannah asked what language Daniel was speaking, and Paul replied that he was speaking Russian and had mentioned something about Tunguska.
Later that day, Hannah entered Daniel's cabin and found him stressed, expressing his concerns about sanity and pleading with her to let him get his medication from his apartment. Hannah reluctantly gave in to his request and handed him a white hooded jacket, so that he could blend in with the other Assassins as they left the camp.
As Hannah was complaining about Daniel's filthy apartment, Daniel searched through his cupboards looking for his medication. After he found that there was none left, Hannah tried to comfort him by saying that the Assassins could help him if he let them.
She told him about her history with the Assassins, and that their Mentor intended for "their guy" to win that year's presidential election. Daniel noted that he kept seeing a strangely shaped object during his "visions", which he then drew for her on the fog on his window. Hannah quickly recognized the shape to be one of the Staves of Eden.
Suddenly, Paul burst into the apartment, telling them that he had called Bill Miles, who had come to the conclusion that Daniel was the descendant of Nikolai Orelov, a Russian Assassin who was involved in the Tunguska explosion. At the mention, Daniel experienced another memory of Nikolai through the Bleeding effect, causing him to run out the window onto the roof of the building.
Concerned that he would hurt himself, Paul demanded for Hannah to stop him. They chased Daniel until he finally collapsed on the roof of an adjacent building. As Hannah held Daniel in her arms, he said that he had found his purpose; that he had to find the Mentor.
Supporting Daniel's quest
- "I believe in you, Daniel. We all believe in you."
- ―Hannah talking about Daniel's quest.[src]
Over the next two years, Daniel visited all Assassin camps in the world trying to convince the Assassins of his usefulness to the Mentor, and asking for their support and guidance.
Some time later, Hannah had returned to her camp. There, Paul revealed that Daniel had killed the Mentor, and had revealed his true allegiance to the Templars. Since Daniel knew the location of all Assassin camps, Paul pointed out that they were in danger, and had to abandon the camp. Hannah simply stood in shock, not able to believe what Daniel had done.
Hannah continued to serve the Assassins for the coming years, having successfully eluded the Great Purge. At some point, she became good friends with fellow Assassin Rebecca Crane. In 2011, Templars under the command of Daniel Cross launched a raid on the Assassin hideout Hannah was located in. Hannah stayed behind to give her fellow Assassins time to escape, and tried to reason with Daniel in hopes of returning him to his former self. However, her attempt was unsuccessful, and she was killed by Daniel.
Years later, in 2015, the Assassins used a camera drone named Hannah, one of several drones which shared names with fallen Brotherhood members, during Shaun Hastings and Rebecca's London operations.
Personality and characteristics
- "You may not love the way things are, but at least we got here through free will. The Templar way would have been less... democratic."
- ―Hannah's view on the Assassins.[src]
Hannah was warmhearted and loyal, fully believing in the Assassin cause and showing compassion to those around her. She disliked violence, and as such, worked mainly with computers for her Order.
After Hannah brought Daniel to her Assassin compound, she was quick to trust him and believe his good intentions. She was swayed by his emotional state, and agreed to bring a crying Daniel to his apartment to get his medication, despite her orders to remain in the Assassin compound.
Hannah joined Daniel in his journey across the world to visit the Assassin compounds, fully trusting him, despite many Assassin having their doubts about him. Hearing about Daniel's betrayal later left Hannah speechless and overtaken by emotion, even as the other Assassins prepared to evacuate their compound. She had such faith in Daniel she even decided to stay behind and reason with him, but he killed her.