Should I use a period after titles like "Mrs", "Dr", and "Capt"?
In British English, the abbreviations Mr, Mrs, Miss, Ms and Dr are not followed by a period. In these cases, the abbreviation ends with the same letter as the full word, e.g. Mister / Mr both end in "r". Abbreviations where the final letter is not the same as the word it's abbreviating, e.g. Captain / Capt. and Professor / Prof. should be followed by a period. The following sentence is correct in British English: Let's give a warm welcome to Mr Sherlock Holmes and Capt. John Watson.
In US English, ALL of the abbreviations should be followed by a period, e.g. Let's give a warm welcome to Mr. Sherlock Holmes and Capt. John Watson.