Arnold Robinson is the Senior Analist of FBI San Francisco. He does a some of field work, as well as assisting the other employees of FBI about whatever is going on during a crisis. He has helped Rick Jackson and others save millions of lives. He was first introduced on Day 1, Episode 1.
Days 1,2 and 3
During Days 1,2 and 3, Arnold primarly was only at FBI, and helped stop the attacks that occured.
During Day 4, Arnold was following up a small lead, and found the base of rajeem general Benjamin Tredaku. He later found out that Tredaku was raiding the White House, and told Ralph Wilson of this information. Arnold later helped Rick clear his name for the murder of Michael Harris, and helped Rick break into the African Consulate. He, along side Rick Jackson and Chris Andrews, flew back to San Francisco at the end of Day 4.
During Day 5, Arnold wasn't that vidal, until he was kidnapped by Mohammad Amad so he could be forced to arm the four remaining suitcase nukes. Arnold was tortured brutally, and finally agreed to arm them. Rick Jackson later saved Arnold, and brought him back to the FBI. Later, Arnold helped Rick break into the Russian Consulate to give a private interrogation of Consul Victor Stovitch. Arnold also helped Rick aquire an FB-Sub circuit board when William Henderson was blackmailing him to do so. Arnold helped alot throughout the day, and helped save millions of lives.