- "We're Rangers. Isn't posing a threat kind of the fucking point?"
- ―McKenna (from The Predator)
McKenna first appears after the Fugitive Predator's ship escapes the Upgrade Predator's ship and enters the Earth's atmosphere. At this time, Quinn is on a hostage retrieval mission in Mexico. Wearing a ghillie suit, Quinn is in sniper mode when he suddenly sees the ship crashing towards him. He quickly snipes a cartel member and evacuates his spot at the last second. After calling-in his teammates Haines and Dupree, Quinn finds a bio-helmet and a mysterious wrist gauntlet, which clamps around his forearm. Meeting up with Dupree, the two suddenly see Haines' skinned corpse hanging from a tree, before the Fugitive appears and blasts Dupree's chest with its Plasmacaster. The camouflaged Fugitive prepares to advance on McKenna, when the gauntlet suddenly ejects a small throwing disc that injures the Fugitive and slices Haines' corpse in half. McKenna watches as the blood from Haines' bisected corpse drips onto the camouflaged Fugitive's face and slowly reveals its true form. When its eyes open, McKenna grabs his knapsack with the bio-helmet inside, and runs out of the forest as he sees a helicopter pass overhead.
McKenna next appears in a small village in Central America, where the gauntlet has come off his wrist. As government forces arrive, McKenna orders a bartender to mail the equipment to his ex-wife's house. Before he is taken in, McKenna intentionally swallows a spherical gadget that allows the Predators to camouflage.
At the US Department of Defense's base in Chattanooga, Tennessee, McKenna is being evaluated on the mission by a psychiatrist, while government agent Will Traeger and his partner observe through a window. Detailing his alien encounter and accusing his psychiatrist of trying to hide government secrets, McKenna is put aboard "The Loony Bus", where several other soldiers are deemed "insane". He meets his fellow bus mates Nebraska, Coyle, Baxley, Lynch and Nettles.
The bus is redirected to the base of Project Stargazer: a top-secret CIA project lead by Traeger, to study a live Predator specimen. When the captured Fugitive Predator escapes the base, Quinn teams up with the Loonies to seize control of the bus and take kill it. The Loonies meet evolutionary biologist Casey Brackett, and they save her from being killed by a Stargazer operative.
At a bar, the Loonies learn that Casey was an "on-call" in case there was ever extraterrestrial contact. They also learn determine that the Fugitive Predator is heading for his ex-wife's house, because he mailed its gear there. After the Loonies meet his ex-wife Emily McKenna and learn that the gear is missing, Quinn determines that his son, Rory McKenna, has gone trick-or-treating with the gear, mistaking it for a Halloween costume.
McKenna arrives at Rory's school just in time to save him from a pack of Predator Dogs. The two reunite after McKenna blows one up and Nebraska lobotomizes the other with a drill gun. Their moment is short-lived, however, as the Fugitive Predator suddenly appears and threatens Nettles, Casey and Rory. Baxley's tourettes accidentally distract the Fugitive, giving McKenna enough time to grab his gun and briefly injure it. McKenna, Casey and Rory escape inside the school, where the Fugitive finds them and choke holds McKenna. McKenna gives it a device from the gauntlet, before the Fugitive Predator is suddenly grabbed and pulled out the window. A second, larger Upgrade Predator reveals itself and kills the Fugitive while the Loonies escape. The Loonies take refuge at an abandoned barn.
They fight the Upgrade Predator after that, but cannot stop him from kidnapping Rory, which he does because of his brilliant abilities. Still they manage to damage the ship, when it tries to leave the planet with him. Then, with the help of the other Loonies who all die, his son and Casey, McKenna manages to defeat and kill it. Later he takes over the Stargazer Project and makes sure his son is with him helping him in the project. When they find out the Fugitive Predator has left a present for human so they can defend themselves against the Predators and finds out it´s a suit called Predator Killer, he gladly decides to use it.
McKenna's main sniper's weapon was a Springfield Armory M1A fitted in a JAE-100 G3 precision stock with a forest camouflage paint scheme, although he lost the rifle during his encounter with the Fugitive Predator in Mexico. During his subsequent battles with both the Fugitive and the Upgrade Predator, he carried a War Sport LVOA rifle that he kept at his home as his primary weapon. His preferred sidearm was the FN FNX-45, and he also briefly used a SIG Sauer P226, a Heckler & Koch MP5A3, a Milkor MGL grenade launcher and a Glock 17 during his battles with the Predators and Stargazer personnel.