While travelling in a van, the Assassins were attacked by Templars. After they fended off the attack, Geier suggested that Abstergo had planted a bug on Lucy Stillman or Desmond Miles, saying that was the reason they were found. However, the Assassins couldn't find a bug, and they resumed their journey.
After Desmond went to relive more of his ancestor Aquilus' memories in the Animus in the van, he discovered the meaning behind the phrase "The eagles don't fear the vultures, but they have to start being cautious", realizing that "Geier" was German for "Vulture". While they were having a discussion, Desmond asked for Lucy's gun, and shot Geier in his leg. After showing a phone he took from one of their Templar attackers and pointing out that a phone call was made to Geier, he finished Geier with a bullet to the head.