Danner was born on Earth to John and Marie Danner in 2327. He later had a younger sister named Petra. Due to his father's job as a mineral trader throughout the Alpha Centauri system, Danner lived a nomadic childhood.
John was later killed over a black market deal, leaving his son the breadwinner for his mother and Petra. During his teenage years, Danner joined the UCA, possibly to avoid gambling debts. He fought in the conflict between Earth and the middle colonies.
During his service, Danner did his best to distinguish himself in several colonial campaigns, including a campaign in the Beta Hydri system and the unrest in Delta Pavonis. Danner was dishonorably discharged from the UCA after a failed peace keeping mission resulted in civilian deaths in 2351; in which Danner's unit were blamed for the deaths by the UCN. This incident left Danner resentful toward Earth authority. With limited prospects, he went on to work for Anders Benoit's Phantom Talon Corp.
After joining the PTC, Danner was involved and saw action in disputes on the breakaway colonies of the ICSA.
"Welcome to the war zone, Danner. This is the big one. The jackpot. The ISA are desperate - running out of men and equipment, fast. They're ready to pay big bucks for our brand of elite firepower. ...for hard-ass sons of bitches like you. Good to have you back on the payroll. One man's cause is another man's grievance. Either way, it's a chance to make money..." ―Ander Benoit
"Thanks to us, Admiral Grey's alive, and Kratek left the city with his tail between his legs. The Higs are on the back foot. Grey wants to take the fight to them. The ISA took down a cruiser in the bay. The Higs are trying to repair it -- sucking half the city's power from the grid in the process. Once it's operational, they'll use it to ship stolen ISA weapons technology back to Helghan. And here's the icing on the cake -- that cruiser carries the codes used to encrypt transmissions between the Helghast fleet. Securing those codes could give the ISA the edge they need. Your job is to hack the comms servers for the codes, then scuttle the cruiser." ―Ander Benoit
"Nice work, Danner. Taking out those Arc Cannons and cruisers opened a window for the ISA invasion. And while those poor S.O.B.s are storming the beaches, we have a chance to make some easy money -- away from the front line. The Vektan Ambassador and his family are under house arrest in the Embassy. Having a Hig bitch wife kept him alive this far, but now the invasion started it looks like his 'immunity' is about to run out. The Ambassador and Admiral Grey go way back. Plus it was intel he leaked that helped save her life back on Vekta. She wants him and his family brought to safety. There's more. A Helghast scientist approached the Ambassador, looking to defect. This guy's close to Kratek -- if he's in there, Grey wants him too. The family are hunkered down in the Ambassador's residence, along with their Helghast bodyguard. The building's under lockdown, so you'll have to find a way through to them. I'll set you down outside the Embassy and watch the LZ while you're inside. Let's keep this one simple, Danner. Quick in and out, cash the check." ―Ander Benoit
"You're lucky to be alive, mercenary. There are so many reasons why I should have you killed... ...only one why I should not. Doctor Savic is being interrogated at the Vektan Embassy. Admiral Grey has made it her center of operations. Now she has the 'trigger' she is sure to go after the virus. Savic knows the location of the secret facility where it is stored -- and he is not a brave man. Once Grey has the virus, she'll use the trigger to create a deadly bioweapon. Then she'll watch all Helghan die with a smile on her face. You will stop her. Our forces are tied up fighting the ISA invaders in the city. You know the layout of the Embassy -- you must get to Savic and find the stolen 'trigger'... kill ADmiral Grey if you get the chance. The building's heavily defended, so the dropship will deploy you to the roof. Ground troops should break through in time to extract you. I know you only soldier for profit, and I don't have time to 'persuade' you otherwise. You'll get your blood money..." ―Vyktor Kratek
"Grey got what she wanted at the Embassy -- you failed to stop her. Now she's on her way to seize the virus. The ISA have already overrun the secret facility where it's held. Grey has the trigger -- hidden inside the child himself. Now she'll use it to activate the virus and create a bioweapon. She's well prepared -- ready to deploy the virus as soon as it's made contagious. There's only one chance of stopping her... Savic didn't give Grey the code to the vault where the virus is stored — only you know what it is. That's why you're still alive. It will take Grey's men time to drill their way in. You must get inside first. The dropship will get you on board. My men will help you take control of the facility's defenses. Then you will get to the vault and open it... ...obtain a sample of the virus for me, and set charges to destroy the rest. There's one more thing you must do for your money, mercenary. This time Admiral Grey dies..."―Vyktor Kratek
"The ISA set charges. You triggered them when you blew up the Vault. The facility is drifting out of control. But at least Grey is dead -- and you have the virus. If you want to leave tehre alive, you'll find the boy and bring him and the virus to me. I'll be waiting on deck while my men deal with the ISA left inside the facility. [Transmission jammed.] Pardon me butting in, Danner. But you must know -- Kratek will kill you as soon as het get what he wants. He's as crazy as Grey was. Once he has bioweapon, he'll use it. The war will be over in no time -- which is ve-ry bad for business. On the other hand... ...get the boy out of there and destroy the virus, I cut you a deal. Grey left the kid outside when she went to the vault -- the explosion took care of the guards, but it took out Grey's Intruder too. You'll have to get to the landing deck and steal Kratek's dropship -- it's your only way out of there. It won't be easy. Kratek's men will be coming for you, and the place is about to crash and burn. But it'll be worth it! This way, neither side lose out -- and we win big. Watch yourself, Danner. You've only got one friend left in there -- and he's ten years old..." ―Vyktor Kratek and Blackjack