Iris was murdered by the Reverse-Flash, via a vibrating karate-thrust to the brain. Her biological parents sent Baby Iris forward in time with the help of John Fox, causing a bit of a time paradox but it all worked out eventually.

Then Barry tried to marry again, to somewhat of a nonentity named Fiona Webb, who Reverse-Flash tried to murder on their wedding day (that's kind of his thing, murdering Barry's ladies). Barry broke Zoom's neck just before Zoom could reach her, killing him, and _that_ led to the interminable Trial of the Flash.