Story Structure: Examples of Option Locks

Optionlock as the Limit — The story is forced to a conclusion because options run out. For example, a lawyer has a limited number of witnesses she can try to persuade to testify in order to clear her client; there are only a certain number of soldiers who posses the combination of skills necessary to infiltrate the enemy base and destroy their secret weapon; etc.

Excerpted from
Dramatica Story Development Software