| One time use|
|(page 4, column 10, line 6)
Plan C is an unlockable activated item added in Afterbirth †.
- Upon use, deals 9,999,999 damage to every enemy in the room, then kills Isaac 3 seconds later.
- Plan C does not kill both phases of bosses like The Lamb, Hush, Ultra Greed, and Mega Satan, and is most useful when used during the last phase of these multi-phase bosses. After killing bosses, however, you will not be able to reach the chest or next floor in time. The kill still counts as a victory for Completion Marks, but the run will still end without extra lives.
- While using this will technically kill Delirium, his death animation takes longer than 3 seconds, meaning you will die first and it will not count as a Delirium kill. Having extra lives that re-spawn your character outside the room will not help either; you must fight Delirium again.
- Invulnerable enemies and closed Hosts will not be killed by Plan C.
- Isaac's last will will show his last damage source as the cause of death, not Plan C. If Isaac has not taken damage or lost health from any source, Isaac's face is shown.
- Even if Isaac enters a trapdoor immediately after using Plan C, he will still die after arriving at the next floor.
- Plan C has an 80% decreased item pool weight, making it less likely to appear than other collectibles.
- Extra life items ( Dead CatSets the amount of red heart containers to 1, but gives Isaac 9 extra lives. After dying, Isaac is teleported to the last safe room. New heart containers can be obtained after picking up this item, but after each death, the number of heart containers is set to 1 again., 1up!Gives an extra life. Upon death, you will respawn in the previous room with full health and lose the 1up!., etc.): Allows Isaac to continue after using Plan C.
- Lazarus' RagsUpon dying, resurrect as Revived Lazarus with one heart container and Anemic item.: Allows Isaac to continue after using Plan C. Unlike other extra life items, Isaac respawns in the same room (as Lazarus Risen).
- This is a reference to the "Morning After" pill that prevents a pregnancy, commonly referred to as "Plan B". It's also a reference to a "cyanide pill" that is fatally poisonous, and can be deliberately taken to commit suicide. It's likely that the item is called "Plan C" because it is too late for a "Plan B" to prevent Isaac from being born; so the "next best thing", Plan C, is for Isaac to kill himself. Additionally, the initial of C is likely a further reference to the aforementioned cyanide pill.
- Before the Cathedral is unlocked, the viable method for this item would be to use it on Mom's Heart (or It Lives), which would be another joke around "Plan B."
- This item is found in more item pools than any other item in the game.
- Plan C's sprite is a red-tinted Forget Me NowWhen activated, the level ends and is freshly regenerated with new rooms, monsters, and items. Disappears after use..