The Mad Doctor is the name of the man who processes Thick Blood into stat-augmenting serum. He chiefly does this by operating a machine that seemingly strains the plasma out of the blood; however, it is a somewhat sensitive contraption, as it can only handle so large a volume of the fluid before breaking down. This causes the Mad Doctor to attempt to correct the problem, hit it futilely, and then give up, hanging an "Out of Order" sign across it and walking away.

Thick Blood does not carry over to the next stage, so it is in the player's best interest to reach this breaking point every single time. The machine's limit does increase each stage, allowing the player to become successively more powerful over the course of the game, but there is still not enough serum in the game to power up every character fully. This leaves leveling, to some degree, up to the player's personal discretion.

The Mad Doctor resides on Channel B. Some players interpret him as yet another iteration, aspect, or owned soul of Harman Smith. See also Graham MacAlister, Harman's physician in life.

killer7 characters
The killer7 Harman Smith · Garcian Smith · Dan Smith · KAEDE Smith · Kevin Smith · Coyote Smith · Con Smith · MASK de Smith
The Smith Syndicate Samantha Sitbon · Christopher Mills · Iwazaru · Kikazaru · Mizaru · Travis Bell · Kess BloodySunday · Yoon-Hyun · Susie Sumner · Mad Doctor · Gary Wanderers
Heaven Smile Kun Lan · Heaven Smile · Gatekeeper · Kenjiro Matsuoka
Angel Angel · Red Gunners · Bianca · Pussy
Sunset Toru Fukushima · Young Guys ×3 · Jean DePaul · Julia Kisugi · Spencer · Hiroyasu Kurahashi · Shinya Akiba · Hiro Kasai · Mary · Plenty
Cloudman Andrei Ulmeyda · Stacy Spangles · Cult Member · Old Man · Man in Photograph · Drug Store Employee · Postman · Security Guard · Gabriel Clemence · General Lynch · Helga
Encounter Curtis Blackburn · Curtis's Bitch · AYAME Blackburn · Pedro Montana · Mary Montana · Archangel · Xenia
Alter Ego The Handsome Men · Steve Thunderson · Trevor Pearlharbor · Singer · Mithra · LOVE Wilcox
Smile Linda Vermillion · Edo Macalister · Dimitri Nightmare · Holbert · Emir Parkreiner · Benjamin Keane · Greg Nightmare · Solitaire
Lion Last Shot Smile
And... Johnny Gagnon
Hand in killer7 Jaco Checkbox · Jim Townsend · Susan · Graham MacAlister · Jack Foley · Mr. A
killer is dead Shigeki Birkin · Samayoru · Mario Castiglioni
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