An interesting piece of grammar, by adding (으)ㄹ 까 봐(서) to a verb or adjective stem, we say ‘For fear that A/V’ or ‘In the case that A/V’. Often the (서) is left out when speaking.
시험이 어려울까 봐 공부를 열심히 했어요.
I feared the test would be difficult, so I studied hard.
수업에 늦을까봐 일찍 일어났어요.
In the fear I would be late to case I got up early.
비가 올까 봐서 우산을 가지고 왔어요.
I brought an umbrella in case it rains.
For further explanation and examples, check out this clip from Let’s Speak Korean: