Army of Frankensteins

Virginia, a former slave and Solomon's girlfriend, is captured by Frankenstein in a hot-air balloon. During their escape, she shares her experiences of slavery and explains why the Union fight matters to her. Moved by her story and her courage, Frankenstein switches sides and agrees to help the Union cause. This change also causes the other Frankenstein duplicates to ease their aggression.

Dr. Finski reveals that the portal opened because of the lightning strike combined with the regeneration serum and the experiment. He explains that the only way to reopen the portal and return to their own time is to kill the original Frankenstein, whose life force is tied to the portal. However, Finski dies from his battle wounds before they can formulate a plan.

After the group is captured and being returned, Solomon is attacked by the cat-beast that Lt. Swanson earlier transformed using the injector. The transformed cat mauls Solomon during the journey, tearing off his left forearm. Later, Igor's disintegration ray replaces the missing arm.

Earlier, Swanson tests the injector on a cat, transforming it into a beast that roams the woods.

After observing the original Frankenstein's strength and power from the injector, Captain Walton becomes obsessed with creating an even stronger soldier for the Confederacy. He orders Swanson to inject him, transforming into a larger, more formidable Confederate monster that he believes will win the war for the South.

Swanson previously tests the injector on a cat, demonstrating its transformative power.

Before leaving for the capital, Igor secretly hands Solomon a bag and tells him not to open it until after he's gone. The bag contains a metal rod meant to be placed in Solomon's grave during a stormy night. A lightning strike later activates the regeneration fluid inside, bringing Solomon back to life, revealing Igor's role in ensuring Solomon's survival across time.

At Ford's Theatre, Frankenstein takes the bullet meant for Lincoln, saving the President. However, the shot staggers the dying monster, and he loses his balance, toppling the balcony above. The balcony collapses and crushes Lincoln beneath the debris. So Frankenstein's heroic act to save Lincoln ironically causes Lincoln's death anyway.

The other Frankenstein duplicates are created from the original monster and share a mystical connection to him. When Maggie stabs the original Frankenstein and he dies at Ford's Theatre, this connection is severed, causing all the duplicate Frankensteins to vanish instantly.

During the climactic battle at Ford's Theatre, Booth attempts to flee after Walton is killed. Solomon, now equipped with Igor's disintegration ray built into his prosthetic arm, fires at Booth and disintegrates him completely before he can escape.

Maggie is Virginia's sister. During the massive battle, she seeks revenge because the original Frankenstein killed her soldier boyfriend earlier in the conflict. Her personal grief drives her to attack Frankenstein, but the Confederate monster uses this distraction to disable Solomon's ray gun and kill Maggie.

Dr. Finski's team removes one of Alan's eyes and grafts it into the Frankenstein monster. When Igor injects the regeneration serum, Alan is present in the room, and his unique physiological connection to the creature, through the grafted eye, triggers the awakening process. A lightning bolt then overloads the system, fully bringing Frankenstein to life.

Alan's eye is grafted into the monster before any attempt at reanimation.

When Solomon rescues Alan on the Civil War battlefield, he discovers Alan is his distant ancestor. At the end of the film, a genealogy search reveals that Solomon married Virginia and even adopted Igor, making Igor Alan’s great-great grandfather, explaining why Alan was pulled through time to meet his ancestor.

After Alan returns to the present and proposes to Ashley (who declines), he looks at a $5 bill and sees Frankenstein's face etched onto it. This surreal detail suggests the events of the movie have somehow altered reality, leaving a permanent mark from his time-traveling adventure.