In My Humble Opinion: The best thing to come out of the Thor movies has been Tom Hiddelston’s portrayal of Loki. Enjoy!!!
Very long ago, Bor, father of Odin, vanquished the Dark Elves led by Malekith, who sought to return the universe to its state before creation using a force called the Aether. Fighting off Malekith’s enhanced warriors, the Kursed, Bor contains the Aether within a stone column. Unbeknownst to him, Malekith, his lieutenant Algrim and others escape into suspended animation. In present Asgard, Loki stands before Odin in shackles and is sentenced to imprisonment, while Thor, alongside warriors Fandral, Volstagg and Sif repel invaders from Vanaheim, home of their comrade Hogun; it is the final battle in a two-year war to make peace in the Nine Realms. In London, astrophysicist Jane Foster, who has not seen Thor in that time, attempts a lunch date with a man named Richard but is interrupted by her intern Darcy Lewis. She takes Foster to an abandoned factory where the laws of physics are upended in spots and objects disappear into thin air. Foster, after bringing her own scientific equipment to the factory, is sucked into a vortex where the Aether enters her.
The Asgardians learn a rare alignment of the Nine Realms is imminent, and at spots where the Realms touch, as at the factory, portals are created. When Heimdall tells Thor that Foster is no longer on Earth, Thor begins a search for her there. She has awakened in the factory after hours in the other realm, and finds herself releasing powerful energy when a police officer on the scene touches her. Sensing the force’s unearthly nature, Thor brings Foster to Asgard, but its physicians cannot remove it. Odin realizes she is the Aether’s vessel and this heralds a catastrophic prophecy. Frigga—Odin’s wife, Thor’s mother and Loki’s adoptive mother—takes Foster under her wing. In holographic form, Frigga visits Loki in his cell to convey her love and disappointment.
Malekith and his forces, awakened by the Aether’s release, turn Algrim into a Kursed and attack Asgard. Malekith and Algrim kill Frigga while searching for Foster, and are attacked by Thor, forcing their retreat. Thor is ordered to remain and protect Asgard rather than pursue revenge. Following Frigga’s funeral, Thor decides to take Foster from Asgard to lead Malekith away. He reluctantly teams with Loki, who knows a secret portal to Malekith’s world. With Volstagg and Sif guarding his flank, the two commandeer a Dark Elf spaceship and escape with Foster.
On Earth, Lewis learns that her colleague Dr. Erik Selvig has apparently gone mad and has been institutionalized after attempting to conduct scientific experiments at Stonehenge while naked. She has Selvig released from a hospital’s mental ward with the help of her own intern, Ian. Thor, Loki and Foster confront Malekith and Algrim on Svartalfheim, where, after a hoax in which Loki appears to betray Thor, Loki sacrifices himself to keep Malekith from retrieving the Aether. It is to no avail, as Algrim batters Thor and Malekith takes the Aether from Foster. Thor and Foster return to Earth after stumbling upon a portal between realms. The battle shifts to London, where Malekith, in a towering space-vessel, will use the Aether at the exact moment and place of the Nine Realms’ convergence to destroy the universe and restore the dark-energy state in which the Dark Elves thrive. As Thor battles Malekith, Foster and Selvig use devices they have constructed to shift energy where the Nine Realms meet. At the last moment, they transport Malekith and his ship back to Svartalfheim, where the crumbling ship crushes him.
In Asgard, Thor declines Odin’s offer to take the throne and tells Odin of Loki’s sacrifice. As Thor leaves, the image of Odin reverts to the true form of shapeshifter Loki, who, disguised earlier as a warrior, has usurped the throne.
In a mid-credits scene, Volstagg and Sif visit the The Collector and entrust to his care the Aether, commenting that—with the Tesseract already in Asgard—having two Infinity Stones so close together would be dangerous. As they leave, the Collector remarks “one down, five to go.” In a post-credits scene, Foster and Thor reunite on Earth.