One of the many, many things troubling Wes "Sad Puppy" Gibbins on How To Get Away With Murder was the circumstances behind his mother's death a decade ago. All Wes remembers is walking in on her suicide attempt, finding her bleeding from the neck, and calling the police. Of course, he soon learns Annalise was somehow involved and even contemplates whether he himself could have been responsible, and his child-brain simply blocked the killing out of his memory. So how did Wes' mom die on How To Get Away With Murder? In this case, the suicide really was as it appeared. But that doesn't mean Annalise was totally innocent.
After convincing Wes' mom, Rose, to testify in villainous rich dude Wallace Mahoney's son's murder trial (he was accused of killing his girlfriend), Annalise is left in a lurch when Rose backs out in fear at the last minute. It's eventually revealed that Wallace has been raping Rose, who worked as his cleaning lady, for years and that he's actually Wes' father. Annalise gets Eve to threaten Rose with deportation should she refuse to testify, and, stuck between a threat to her personal safety, and possibly being separated from her son, Rose takes her own life. The catch is, she does it in front of Annalise. Just before stabbing herself in the neck, Rose tells Annalise to take care of Wes. Annalise, extremely pregnant, starts to call 911, but then hesitates, realizing the positive effect it might have on the trial if Rose were dead.
Annalise hears little Wes coming and bolts out of the kitchen before she's spotted, letting him find his own mother bleeding out on the floor, before escaping the apartment without being seen. Of course, we now know that Annalise kept her promise to Rose, making sure Wes got into Middleton off the waitlist, and putting him in her prestigious intern group, the Keating 5. She's doing all she can to ensure Wes has a leg up in the legal world, which may or may not make up for the fact that she literally let his mom die. For her part, Annalise tried to confess her wrongdoing to Wes at his apartment door, but it turns out the person inside wasn't really Wes at all. Instead, she had spilled her guts about all of this to Philip Jessup.
Wes has sorted out Eve's involvement in his mother's death, and the last we see of him is Wes confronting Wallace Mahoney before an off-camera shooter guns him down. As for whether or not Annalise and Wes' relationship will survive the fallout of the revelation, we'll have to wait for the Season 3 premiere on Thursday, September 22nd to find out.