The X-Men franchise has issued a new status quo into the Marvel Universe with the launch of Dawn of X, uniting the mutants of the world under one banner in their own sovereign nation of Krakoa. But some mutants are still left wanting, not sure of their place in this new status quo. This is especially true of Kwannon, the psychic ninja whose body was inhabited by Betsy Braddock for decades, but who is now back in control. The character previously shown to be an assassin, but the first issue of Fallen Angels reveals that she has a past that has evaded her until now.
In the issue by Bryan Hill and Szymon Kudranksi, Kwannon reveals that she once had a child who was taken from her during her training to become an assassin — and now that child has been reconditioned to become a servant for the viral entity known as Apoth.
In the comic, Kwannon learns of Apoth attacking public places and resulting in the deaths of many people. There's a religious aspect surrounding this new entity, as rumors state that it will become a "new god" in the wake of the mutant exodus from the rest of the world.
Apoth is basically spreading its "message" by spreading a new designer drug called Overclock, which is described as bypassing "the need for chemicals and boosts the endorphin centers of the brain," but that it's possibly lethal and forces you to take out as many people as possible.
The comic begins with an example of this, showing Kwannon's child under the influence of Apoth and Overclock, with a black liquid pouring out of her eyes. She enters a crowded subway with a device attached to her temple and immediately fights her way onto a train, taking out the guards and the conductor before sending it crashing, killing many people in the process.
When Kwannon learns it was her daughter, she is immediately driven into a rage to determine who and what Apoth is. She tracks the source down to a small farm outside of Tokyo where a group of children are being held in a barn. Though they seemingly appear to be healthy aside from the black ooze and the devices on their heads, the children all die in front of Psylocke — all but one, and Apoth's voice begins to use the child as a vessel.
Psylocke immediately tells the entity that she is going to track it down and kill it, still harboring resentment for the apparent manipulation and death of her own daughter. But Apoth simply taunts her, killing the last child leaving Psylocke without any leads. Despite this, she makes it her mission to get revenge on Apoth before it can hurt any more children.