This article discusses the role of historical closure in conflict resolution and reconciliation, departing from the example of the Polish Round Table negotiations in 1989. The concept of a “thick line” (“Gruba kreska” or “Schlussstrich”) was used in several historical contexts, showing the intention to detach from history when resolving pressing current societal issues. Historical evidence suggests that it was an intentionally chosen strategy by both sides taking part in the Round Table negotiations in 1989. Historical closure is known to have good consequences for building mutual trust, improving attitudes and making contact interventions more effective in improving intergroup relations. This is mostly attributed to the fact that historical crimes can have a long-standing impact on intergroup relations: past victimhood and perpetratorship lead to current grievances, denial, and mistrust. Only when these historical roles are overcome can both parties achieve any agreement. At the same time, historical closure breeds a sense of injustice among political followers and gives birth to numerous conspiracy theories. This article analyzes these problems in the Polish context and beyond.