the crucial moment;the critical juncture ? 他在～接到上級的指示，轉(zhuǎn)入地下。At the crucial moment he got the instruction from the higher authorities and went underground.
緊要關(guān)頭jǐn yào ɡuān tóu
緊急而重要的關(guān)鍵時刻。critical moment, crucial, the critical juncture, in a pinch