 Enterprise is encountering all different kinds of minor malfunctions. When the crew find out the problem lies with the plasma exhaust, they discover they have a stowaway. The Xyrillians have a problem with their warp drive and by using Enterprise  warp drive they tried to recharge their teraphasic coils. Trip is sent to help fix their engine and meets up with Ah len, one of their engineers. The two seem to be getting along very well. Trip is able to make repairs, but shortly after the Xyrillians left, he notices a strange bulging on his arm.