In 2008, shapeshifting Skrulls infiltrated Earth society by posing as humans - even superheroes. The Skrull empire was defeated and eventually combined with the Kree empire in an alliance that is allied with Earth.
Nevertheless, there's another Secret Invasion unfolding on Earth, and the new Skrull invading force has already replaced an Avenger.
In fact, they've replaced more than one.
So which Avengers are Skrulls, and what does it mean for the Marvel Universe? We'll break it down.
Spoilers ahead for Secret Invasion #2(opens in new tab)
Secret Invasion #2 from writer Ryan North, artists Francesco Mobili and Jordie Bellaire, and letterer Joe Caramagna picks up where the first issue of the new limited series left off, with Maria Hill having captured a Skrull who was impersonating Nick Fury despite the Skrull not setting off the technology installed in all SHIELD offices which is designed to detect Skrulls - meaning they've developed a new way to fool Earth technology with their shapeshifting power.
Hill taunts the Skrull into shapeshifting into her, using her outburst as a ruse to get a blood sample from her while she's shifted into human form.
Using the blood sample, SHIELD scientists create a new system for finding Skrulls through their blood. The system is immediately used on the Avengers, with Black Widow quickly being exposed as a shapeshifter and taken into custody.(opens in new tab)
However, there's a fatal flaw in the new Skrull detection system. As Maria Hill uses it to quickly test most of the other major heroes in the Marvel Universe, it's revealed that there's actually another Skrull hiding on the Avengers - and the capture of the Black Widow was all part of their plan to misdirect SHIELD from the other infiltrator.
So who is the other Skrull, and how did they escape detection?
As it turns out, the other Skrull on the Avengers is Tony Stark. And what's more, there are actually multiple Tony-Skrulls working together to impersonate him. And as for how the Tony-Skrull went undetected… we don't actually know yet.
The case of the multiple Tony-Skrulls will continue in January 4's Secret Invasion #3.
Here's everything you need to know about the original Secret Invasion.