Tenses in subordinate clauses

A future verb is necessary for future reference in subordinate clauses if the main verb does not refer to the future.

I don’t know how she will react.
I don’t know where she will be tomorrow.
I am sure she will not come.
A future tense is also used in subordinate clauses when the main verb and the subordinate verb refer to different time points in the future.

I will hide it somewhere where he will never find it. (Two different future tenses)

Tenses after in case, I hope, I bet, it doesn’t matter etc

After in case, we usually use a present tense with a future meaning even if the main verb is present or past.

I have bought a bottle of wine in case James comes.
I always take an umbrella in case it rains.

Present tenses are also used with future reference after I bet, I hope, it doesn’t matter, I don’t care and I don’t mind.

I hope you enjoy your holidays.
I bet he fails his test.
I don’t mind if she stays to lunch.
I don’t care where you go on holiday.

Past instead of conditional

In subordinate clauses referring to the past, simple past verbs are used instead of would + infinitive.

I would follow you wherever you went. (NOT I would follow you wherever you would go.)
In a perfect world, you would be able to do exactly what you wanted. (NOT In a perfect world, you would be able to do exactly what you would want.)