Tony Stark finds himself as a de-aged Loki Odinsson's temporarily designated parental figure, through no fault of his own. Responsible superhero co-parenting doesn't just involve feeding, housing and clothing a tiny Asgardian, it involves rubber ducks, transdimensional vortexes at bathtime, fruit parties, pictures of robots that draw other robots and hoverboards (eventually), as the team keep Loki safe while they look for a solution.

When the Avengers raid a very dubious scientific installation, they come across something they'd never expected to find. Their discovery turns out to be even more surprising than first suspected, and it leads the team - especially Steve and Tony - to some new and very undiscovered territory.