Lethal or poison pill, traditionally carried by spies to be used if captured to prevent their being tortured and revealing secrets. During World War II, some lethal pills consisted of cyanide encased in glass. They could be concealed in a false tooth and worked loose by the agent's tongue if necessary. He would then bite into the capsule, breaking the glass, and would die almost instantly. If the pill broke loose while the agent was sleeping, however, it would pass harmlessly through his digestive track.

Of course, an agent caught with an L-Pill who was unable to use it would immediately be identified as a spy.