Yeah, with the lower case/upper case after dialogue, I knew this was right,
"Don't blink. Blink and you're dead," the Doctor yelled.
But I wasn't sure about this,
"Don't blink! Blink and you're dead!" the Doctor yelled.
I got confused because of the exlamation mark, and I thought it would end the sentence, so thanks for that.
Otherwise I am really good with grammar, apart from the little stuff ups and typos I get from rushing and not paying attention!!!
Again, thank you so much!! I will write more and let you know what I am up to.