3x19 - Mr. Young

In order to make a better first impression on his crush Echo, Adam uses a time machine to travel back to the past to meet her for the first time all over again. After returning to the present he realizes his plan has backfired and he has to time travel back again to repair his relationship with Echo. However, the time travel mishaps multiply and spiral out of control and soon Adam’s meddling in the past has him scrambling to keep from being permanently stuck there.Eventually by the end Adam decides to not change the past and goes back to the present. There Echo tells Adam that she likes him and they start dating. They then kiss. They decide to keep it a secret from everyone else.