Dean Arbagast was a stockbroker.
Arbagast was the stock broker of Gregory Belson, and helped him invest in a new drug making its way into the market despite his reservations. Unfortunately, side effects were discovered, and the FDA put development on hold. Belson had come up 2.5 million dollars short, and Arbagast's accountants were pestering him to get the money. Belson pleaded with Arbagast to stall and give him more time. Arbagast bluntly remarked that nothing could be done and Belson's financial problems were his own fault, telling him "You roll the dice, you had better be able to cover the bet".
Batman and Robin later looked up Arbagast in an investigation into Belson. They tell Arbagast that they suspect Belson is up to no good; to which Arbagast replies it may likely have to do with Belson being in the red. Arbagast gets a phone call from Belson, which Batman traces to an oil rig. Belson tells Arbagast that he will have the needed money in one week. When Arbagast asks how Belson got a tremendous amount of money in such a short amount of time, Belson replies that he just "struck gold", which was true both figuratively and literally as Mr. Freeze discovered a gold vein in the Arctic Circle, which he would give to Dr. Belson after successfully curing Nora Fries of her malady.