вот в чем собака зарыта

• ВОТ ГДЕ <B ЧЕМ> СОБАКА ЗАРЫТА; ВОТ ТУТ <ТУТ-ТО, ЗДЕСЬ, В ЭТОМ> И ЗАРЫТА СОБАКА all coll

[sent; these forms only; used also as subord clause after знать, понимать etc (when 1st var. is used, вот is omitted)]

=====

⇒ (usu. used to emphasize that the preceding context explains the main reason behind sth., or to express the speaker's sudden understanding of sth.) in this (that etc) lies the essence of the matter, the reason for sth.:

- (so) that's what it's all about (what's going on, what lies at the bottom of it etc);

- (so) that's the crux (the heart) of the matter;

- [in limited contexts] there's (herein lies etc) the rub.

     ♦ "Вот где собака зарыта!" - воскликнул он, когда узнал, что на место уволенного без видимой причины Онуфриева принята племянница нашего директора. "So that's what's going on!" he exclaimed when he found out that the director's niece had taken over Onufriev's job after he was fired without apparent cause.

—————

← The Russian idiom is the translation of the German Da liegt der Hund begraben.