Speedy is in and Aqualad is out in Teen Titans 19 (Jan/Feb 69), by Mike Friedrich, Gil Kane and Wally Wood.
The change in creative team for this issue results in a very different looking, and feeling, story for the team. The villain of the tale tries to join Headmaster Mind's crime school right at the top of the story, but gets literally kicked to the curb. Considering what a lame villain Headmaster Mind is, that does not bode well for this guy. Headmaster Mind's foot is really all that is seen of him in this tale, which comes five years after his debut in Justice League of America, but only a couple of weeks before his return in that book.
Speedy returns to the Titans, and makes the moves on Wonder Girl, which seems to upset Robin. By the end of the story, Speedy and Wonder Girl have started dating. Robin makes an off the cuff remark about how Green Arrow just dumps Speedy when he heads off to the League, which can be interpreted, looking back, as the negligent way Green Arrow raised him.
The villain in the story captures Wonder Girl and Speedy, and then puts on his Punch costume. The costume does not really suit his style, which involves high tech sound and light weaponry.
It works well enough to cause problems for Kid Flash, Robin and Aqualad when they come in search of their missing teammates. But Punch proves to be pretty poor at one on one combat, and his hired goons are not much better, so the Titans take them all down.
The conclusion doesn't really imply that Speedy will now be a regular member, although that is what occurs. In a very nice touch, Aqualad's departure is directly connected to the ongoing Quest for Mera taking place in Aquaman's book at this time.