Williamson (P) sued Columbia (D) and others for conspiracy to violate anti-trust laws. P amended his complaint and D was the only coconspirator from which P sought recovery. P then sued D (alone) in another action based on the same transactions for antitrust violations against P. The second action was dismissed; based on the statute of limitations that was tried upon a stipulation of fact making it a final judgment on the merits. D then moved for summary judgment in the first action. That was granted, and P appealed.