Breakdown of El inspector investigaba el crimen cuando descubrió que el asesino había escapado.
que
that (relative pronoun, conjunction)
haber
to have (auxiliary)
investigar
to research / to investigate
descubrir
to discover
Questions & Answers about El inspector investigaba el crimen cuando descubrió que el asesino había escapado.
Why use había escapado instead of the simple past escapó here?
había escapado is the Past Perfect (Pretérito Pluscuamperfecto), meaning "had escaped". It is formed with the imperfect of haber (había) and the past participle (escapado). You use it to show that the escape happened before the inspector made his discovery (descubrió).
Why does the sentence use investigaba (imperfect) for one verb and descubrió (preterite) for another?
Is it possible to drop the word que in this sentence, like we often drop "that" in English?
No, you must keep it. While in English you can say "he discovered the murderer had escaped," Spanish requires the conjunction que to connect the main verb (descubrió) to the clause that follows it (el asesino había escapado).
Would the ending of escapado change if the murderer was a woman (la asesina)?
No. When forming the Past Perfect, the past participle (escapado) always ends in -o. It never changes to match gender or number when it is attached to the helping verb haber.