"Tenebrae" is the Latin word meaning "darkness."

The service involves segmented reading of John's story of the trial, sentencing, execution, death, and burial of Jesus. After each segment of the story is read, a candle is extinguished. After the fifteenth reading, which confirms that Jesus had died on the cross, the last of the 15 lit candles may be extinguished or taken away, and a loud sound (strepitus, in Latin) may be made to indicate the effect of the death of Jesus on the universe. The final story of the burial is read in near darkness, with the only light being used by the reader.

Worshipers leave in silence to ponder the impact of Christ's death and await the celebration of the coming Resurrection.