Captain MacMillan trains Captain Price to be an effective special operative, and is injured during an attempt to assassinate Imran Zakhaev (described below.) Captain Price refuses to leave MacMillan behind and eventually evacuates him from the conflict zone. MacMillan is later revealed to be Baseplate in Modern Warfare 3, the head of the British SAS. Baseplate unofficially aids Captain Price in stopping the ultranationalist Makarov.
Before the Shot
Captain MacMillan is one of the most popular characters in Call of Duty 4: Modern Warfare, although his appearance is strictly limited to the game's two consecutive flashback missions. The flashback is initiated when Cpt. Price discovers that the one who supplied the Khaled Al-Asad's militia with nuclear weapons was none other than Imran Zakhaev, a Russian arms dealer whom he had supposedly killed fifteen years prior. The level starts with the younger Lieutenant Price, on a wet-work assignment to observe a black market arms deal in Prypiat, Ukraine, and assassinate the lead dealer, Zakhaev. Price states during the mission's introduction that this was the first assassination authorized by the British government "since the second World War." Price and MacMillan are outfitted with ghillie suits to help camouflage them in the drab landscape. They silently eliminate guard patrols as they make their way through the deserted city and towards the hotel from which they plan to carry out the assassination. When multiple targets must be taken out at once, MacMillan often lets Price choose which one he will shoot, while MacMillan, once in position, fires at about the same time. When sneaking through an area filled with empty cargo containers, MacMillan instructs Price to stay back while he eliminates the next patrol. This commences one of the game's most memorable moments, with MacMillan running up behind the guard, quietly shouting "Oi, Suzy!", and hitting the guard with the butt of his rifle. Shortly afterward, the two-man team reaches their destination and sets up to wait.
After the Shot
At the beginning of the second flashback mission, MacMillan instructs Price on how to correctly fire the Barrett .50 caliber sniper rifle in order to take out Zakhaev. After the shot is taken, MacMillan remarks that it was a miss, but took off Zakhaev's left arm and that the blood loss should be enough to kill him. Having been located by a patrolling helicopter (the pilot of which Price then shot), the two rappel down the building as it is fired upon by other helicopters. The men, curiously, run right past the rebels coming after them, who are probably dumbfounded to see giant, shaggy beasts sprinting toward them. After heading through some apartments, and being given a narrow window in which to get to the extraction point, they proceed into an open playground between buildings, and are fired upon by an attack helicopter. They disable it with some well-placed shots, but it comes crashing onto their position. While trying to run away, MacMillan falls and is nearly crushed by the chopper when it slides along the ground. However, it stops its slide just before reaching him, although the force of impact and the fall break his leg. From there, Price must carry him over his back, setting him down in order to deal with hostiles and leaving the Captain to provide support fire. Once they reach the extraction zone in an abandoned fairground, Price sets MacMillan down by the Ferris Wheel and then plants claymores and C4 around their perimeter. Waves of enemy soldiers follow into the area, and more are airlifted in via helicopter. After holding off dozens of the soldiers in multiple waves, the S.A.S. transport arrives and releases backup troops to cover the team as they move to escape. Lt. Price once again picks up Cpt. MacMillan, carries him through the now distracted enemies into the helicopter, and sets him down. They then lift off, leaving the rebels and the supposedly dead Zakhaev behind.
Modern Warfare 3
In Call of Duty: Modern Warfare 3, MacMillan appears as the director of the SAS command post Baseplate. Captain Price reaches out to MacMillan after Vladimir Makarov unleashes chemical attacks across Europe. MacMillan is unable to help in an official capacity due to Price's disavowed status, but MacMillan feeds Price information and supplies as Price leads a small, rogue team to stop Makarov.