Someone's got some SERIOUS explaining to do...

Tristan Thompson was caught on camera making out with an unidentified woman at the PH-D Lounge in Manhattan on Saturday night, just days before his pregnant girlfriend Khloe Kardashian is set to give birth to their daughter. The athlete was in the Big Apple with his team The Cleveland Cavaliers for an upcoming game against the Knicks.

In videos sold to DailyMail, you can see the NBA star wearing his hood while leaning in for a kiss from the woman, who had her arm around his neck. It's clear from other photos of the evening that the two were by each other's sides all night long, and even left together!

Making things even more awkward than they already are, paparazzi openly asked him "Where's Khloe?" as he made his way out of the venue with the girl in tow. Yeah, that's what we're all wondering!

Eyewitness accounts of the make out aren't making it any easier for him to explain it away as simply a deceiving camera angle, either.

"I was there and he was on the table right next to us with a group of friends and some girl who he was obviously making out with all night. They were holding each other and it was so obvious. They were there when I got there and they were part of a big group of friends.They were talking and being around each other all night," the person who filmed the clip told the outlet.

"He was texting and talking on the phone and she was obviously looking over his shoulder. Everybody knew who he was. We talked about it and everybody watched them make out several times. I have obviously seen him before and people around me were like, 'That's Tristan Thompson.' I have seen him on TV. I know how he looks like and people were trying to take selfies with him but he didn't let them. I love the Kardashians and I think it's devastating. I really did believe he was a good guy. I feel so bad for Khloé now because she is pregnant and I want her to know but at the same time I don't. I don't think their fans will like what they see," they added.

Our heart goes out to Khloe, this is awful!