After they discovered the breach in their basement, the S.T.A.R. Labs team had Jay Garrick build a device to stabilize it, by using CFL quark matter. Later that day, Harrison Wells traveled through the breach, from Earth Two.
When Grodd returned to Central City, Joe wanted to kill Grodd, but the team instead decided to transport him to Earth Two with the speed cannon, while Barry’s speed rejuvenated. Cisco used the speed cannon to open up a wormhole, which Grodd was able to shake out of, but was eventually hit into by Flash's supersonic punch.
Zoom jumps out of the portal and tells Harry he only has one day left to make a decision on his offer, jumping right back through afterwards.
The Chronicles of Cisco