Mk revealing his true colors to dh could be during the birth of their child. Dh whos obviously very weak at the moment goes through complications and mk is asked to choose between him and their baby in case it gets worse and he chooses the baby. Mk ofcourse insists that both their lives be prioritised and dh not be neglected but dh passes out before hears it. It doesnt even have to be mk who makes the decision maybe dy or other medical staff who says "He's a carrier the baby's life obviously takes more priority" and thats the last thing dh hears so when he wakes up he realizes mk never saw him as anything more than an incubator and thats what encourages him to run away.