Learner96's answer is correct. To give a tiny bit more explanation: The "d'" in question is the word "de" (of or from) with the e removed because the following word starts with a vowel. Literally, it could be translated "who from between us?" which is a perhaps odd way of asking "who in our midst?"
You can contrast this usage with the phrase "Entre nous," which is the french way of saying "Between you and me" (in confidence)