My gf & I were discussing our theories for the story of Vector/Virus a few days ago, & I think we agreed on this theory.
Clear / The Good Doctor (Doctor POV)- The Patient is admitted to a mental institution where Dr. Rex subjects him to electroshock therapy. It's unknown why The Patient is there in the first place, & it seems his own recollection is merely "vague memories of a caved-in broken life". Dr. Rex hopes that the electricity will help bring him back to being a normal member of society (spoiler: it doesn't).
Puzzle Box (Patient POV) - Amidst all the abuse The Patient is suffering, he struggles to piece together the events of his past, & his confusion only makes him feel more hopeless.
Veil (Alternating POV) - The Patient gives into his hopelessness, desperately pleading to be saved by Dr. Rex's experiments. Dr. Rex tries to reassure The Patient that he's safe with him, which gives The Patient a false sense of trust. The Patient then begs Dr. Rex to do whatever it takes to get him back to normal, & so he does...
Nil By Mouth / Host (Patient POV) - Dr. Rex experiments on The Patient further, subjecting him to a machine that can rewrite The Patient's DNA. The Patient thinks that it will be used to fix his brain, but unbeknownst to him, Dr. Rex has no real intention of helping him, & merely wants a test subject for his experiment. The Patient realises this as the machine's process is taking place, which fills him with even more hopelessness than he had before.
A Cell Divides (Alternating POV) - Unexpectedly, The Patient gruesomely transforms into a cockroach, fulfilling Dr. Rex's wildest dreams. Dr. Rex is proud of his creation, & feeling satisfied, he covers up all evidence of the experiment & goes back to work.
10 years later...
Prosthetic (Patient POV) - Out of the rubble, The Patient is finally discovered. He is then recovered back to human form by the scientists who discovered him, but as soon as he's saved, The Patient turns on the scientists & uses their own technology to overpower them. The Patient is angry about what happened to him, & he wants revenge.
Invasion (Patient POV) - Once alone, The Patient uses his stolen technology to develop a virus that will gruesomely transform & then kill anyone who it's exposed to. He plans to use this on Dr. Rex.
Carousel (Patient POV) - The Patient hunts for Dr. Rex. Along the way, he questions his own motives, but ultimately decides that this is what he needs to do to exact his revenge.
The Strain (Patient POV) - The Patient finally finds Dr. Rex, & seeing his face again triggers a flashback of the hopelessness he felt while he was under Dr. Rex's control.
Canary Yellow (Alternating POV) - The Patient then confronts Dr. Rex, telling him that he's the one that really needs psychological help for all his sadistic tendencies. Dr. Rex retorts by exclaiming that The Patient would've lived a boring normal life if it weren't for his experiments. This enrages The Patient, & he injects Dr. Rex with his virus.
Messiah Complex (Alternating POV) - After seeing what he's done, The Patient feels powerful for overcoming the person who put him through so much misery. He thinks of himself as if he's in an ivory tower. He watches Dr. Rex scream "How did I fail, my holy grail?" as he transforms into a cockroach. The Patient taunts him, saying "Careful what you wish for" as he continues to watch Dr. Rex's own experiment used against him. Finally, Dr. Rex dies from the virus, which The Patient celebrates at first, but then Dr. Rex's words from earlier resonate within him, that he wouldn't be who he is without his experiments. He thinks that for Dr. Rex to really die, his experiment must die too, & so he kills himself, jumping from his tower of ivory.
Only Stars (Patient POV) - In his final moments, The Patient reflects on the trauma of his lifetime as he dies, still feeling the anguish that he did back then, but knowing that it will all be over soon.