curtain-up
/ˈkɜːtənˌʌp/noun
in sing.
1- the beginning of a stage performance（舞台演出的）开场：
curtain-up is at 8 pm
晚上8点开场。
1.1
- figurative the beginning of any event viewed as having an element of display or drama〈喻〉开场, 引子：
it's curtain-up for this week's 'rugby review'.
这是本周“橄榄球回顾”的开场好戏。