Your story begins with the last days of a murderous sociopath whose name I can't pronounce.
I'll just refer to him as s'tibron'ganfragdts'chvipl to keep the story simple. s'tibron'ganfragdts'chvipl was a master of amorph immune-system combat.
Immune system combat is always fought hard, fast, and to the finish. But s'tibron'ganfragdts'chvipl took it one step...
Hang on a moment.
If you really want to keep this simple, let's just call him 'killer.' How's that?
Boring, but if your attention span is really that short...