OK, we know that Thor has been given the mortal personality of Jake Olson who died during 1 of Thor's battles. And we know that the real Olson may have been a shady char, and some of Thor's activities have made his 'Jake' also seem dodgy. But in the last issue Loki resurrected the real Jake and made him try to kill someone in front of CCTV. And Thor and Jake met, and the Thunder God followed him up onto a roof where Loki spirited him away.
That issue ended with Mangog stealing the Chalice Of Ruins from Orikal and handing it to his unrevealed master who declared that when he drinks a tear of the Designate from the cup he will gain the power of all-prevailing death. But 1st they must find the Designate before they can unleash Armageddon.
But Thor knows nothing of this last and is about to transport himself to Asgard to seek help/advice on the Olson mystery. However Jane Foster and Jake's fiancee Hannah Fairmont have followed *him* to the roof and stop him. Hannah is convinced Jake's not guilty of anything and accuses Thor of wanting to arrest him, or maybe even throwing him off the roof. Thor says he knows that Jake is innocent of recent things he's been accused of (because of course *he* is Jake). Hannah runs off to tell the police that Thor can vouch for Jake.
Jane knows about Thor being Jake and they both know that the earlier Jake *might* have been crooked so she criticises him for giving Hannah false hope. And now she tells him about the video evidence of Olson trying to suffocate a hospitalised cop. Thor finds all this too confusing and whirls Mjolnir again to create a vortex to take him to Asgard. But Jane leaps in to follow him.
They arrive on the Rainbow Bridge and Jane is once again overawed by Asgard's splendour. But they find it's guardian Heimdall beaten unconscious. They follow a trail of equally fallen bodies including the Warriors 3 and then Sif who is still able to call out to Thor to warn him of someone whose name begins with M. He tells Dr Foster to look after her while he goes to find the threat. But the threat comes to him in the form of the giant Mangog with the power of an entire alien race who were killed by Odin. His anger is reignited at the sight of Odin's son and they battle mightily while Jane carries Sif to safety. Thor asks if Mangog's intent is as before to unsheathe the Odinsword and usher in Ragnarok? Mangog claims that his master's intent is much worse than that, and that master has gone to deal with Odin.
The hooded master is led by Odin's current Grand Vizier Tarakis to Odin. On the way the Vizier reveals that the daily potion he's been giving the Lord Of Asgard to recover his strength (after the battle with the Dark Gods in #4-12) has instead been draining it. Now Odin is too weak to resist giving the villains the Map Of All-Ending hidden in his sceptre, which will lead them to the Designate. The hooded one reveals himself as Thanos (what, you didn't look at the cover, or last issue's next-issue box?) who gloats that last issue's Chalice and this Map give him the power of life and death. He also says this makes up for Odin having defeated him once before. The 2 villains teleport away.
Mangog seems to have beaten Thor and now turns on the 2 females. But of course the Thunder God summons up reserves of willpower and fires a bolt of anti-force from his Uru hammer powerful enough to shatter mountains. Mangog falls. But then he too gets up again to meet Thor's onrush and knocks him down again. He's about to crush the life out of him with his boot when Thanos and Tarakis port in and call him off. Mangog protests but Thanos says they have more important things to do, and all 3 leave.
Odin manifests next to his son and helps him up. He reminds him of the ancient prophecy about the Chalice and the Map, hidden by Orikal and himself. He confesses that both are now in the possession of Mangog ... and Thanos. Thor realises that this danger trumps all and he tells Jane that he must lay aside his mortal life. Which strangely means that he must take time off to use his 2000 Annual to tie up all the loose ends of the Jake Olson story before returning to continue this storyline next issue.
Give that special marvelite a timely gift