Now that I'm no longer half-asleep, I checked the plan over and made some adjustments. Mainly, rather than risk Black Swan making a Espionage 3 roll, it's better if she hides with Lady Leizi and uses the latter's Espionage 8 instead.
That, and I forgot one crucial thing. Black Swan doesn't have Enhanced Senses, so she'll have a hard time spotting Earthen Owl when he does step outside his fortress. In contrast, if she was in ground level with Lady Leizi, she'd be able to spot him well enough.
A OHKO move only works if you can land it, and it can only land if you can see where your target is!
[X] . . . engage and defeat Earthen Owl (DC 12. HIT Check of 6).
-[X] Have Valiant Kabuto organize his loyalists for an attack on the lab while Lady Leizi helps Black Swan set-up a ambush in the incubator building.
-[X] Valiant Kabuto and his loyalists will fight to lure Earthern Owl out of the lab and lead him to Lady Leizi and Black Swan's ambush, whereupon all three will attempt to knock him out in that instant before he can dig underground.
Aa for why set up in the incubator building? I'm hoping that concrete floors are harder for him to dig through than soft, swampy ground. Powers logic could render that null, but we gotta stack as many advantages as we can. Slowing him down by a bit could be the difference between Earthen Owl escaping or not.