Off left side of a plane until it changed and went UP?

Looked up at the moving planes like I do every night when I take my dog out. Noticed a light that I could not decide if it was one light or 4-5 lights? I noticed that a plane with flashing lights approached this object from its left side. There were no blinking lights on it. All of a sudden, it started to go up. In a matter of 5-10 seconds, it went straight up until it was gone. The plane that had approached was still on course and clear. This light, or cluster, changed course and went straight out into space? It moved wrong when I first noticed it. Then it was not blinking. Most of all, I reiterate that it went from bright to dim, dimmer, and then started to disappear as it got smaller? Might or might not have been more than one when I first noticed. I want to say no, but my memory believes there was 4-5 to start with. Only one was real bright to start?