Events took an unexpected turn.

事情发生了波折。

《新英汉大辞典》

This is an unexpected turn of events.

情势的转变出乎意料。

youdao

Matters have taken an unexpected turn.

事态起了意想不到的变化。

youdao

My second brother was at a loss for words at such an unexpected turn of events.

NPR: Literature and Lullabies from the 'Axis of Evil'

However, within one minute of the break, the script for Wenger's high-fliers took an unexpected turn for the worse when they were reduced to 10 men.

BBC: Arsenal 2-0 West Ham

The trial also took an unexpected turn when Gabriele complained of the conditions in which he was held by the Vatican security force after his arrest on 23 May.

BBC: Pope ex-butler Paolo Gabriele jailed for theft