The third and final book of The Milkweed Triptych
Necessary Evil contains examples of:
- Alternate History: Another alternate history - an in-universe alternate timeline from the alternate history of Bitter Seeds. In this one, Gretel makes sure the war mostly plays out like in our history.
- Alternate Timeline: Gretel's plan was to create a timeline in which the Eidolons do not kill her or humanity.
- Brought Down to Normal: Gretel, and twice to add insult to injury; once, when the interference of two timelines stops her predicting that Liv would be rescued from the bombing of Coventry, and finally when she has her wires removed by both Marshes at the end of the story.
- Go Mad from the Revelation: Gretel, when she realizes that she no longer has perfect control of the timeline.
- I Reject Your Reality: After 7000 heartbeats in close proximity to an Eidolon, Marsh2 starts losing his grip on how reality actually works.
- The Mole: Will becomes this for Marsh1 in Milkweed.
- My Future Self and Me: 2 × Raybould Marsh.
- Reality Warper: The Eidolons. Shown in detail when Will summons an Eidolon for Marsh2 in Berlin.
- Stable Time Loop: ... sort of. When Marsh1 tries to shoot Marsh2 in the knee and fails, their knee pain suddenly goes away.
- Time Travelers Are Spies: Marsh1 ends up in wartime London with another man's wallet and no period currency. Naturally, he's suspected of being a German spy.
- Trust Password: Needed to enter Milkweed. Fortunately for Marsh1, they're the same as in his timeline.