Barney and Diane ask George to be their sperm donor and are thrilled when he appears to accept. But George is worried about finding a new HQ for his rocket after an explosion at Mission Control. They go to the carriage works, but things don't go to plan with either the rocket – or the plans for fatherhood. In the midst of an explosion at Mission Control, Barney asks George to donate sperm. George is shocked and also threatened with arrest for keeping hazardous chemicals in his shed. Desperate for a child, Barney tells an excited Diane he thinks George will help. George goes for extra lessons with Tom's teacher Pam in a bid to improve his reading, but his mind's really on finding the right mix of fuel for Bethan Two and a new place to carry out his rocketeering. Along with Barney, Huw, Lloyd and Tom, they head for the Aber Ivor Carriage Works where Shiner is on night security duty. He reluctantly lets them in. The next day, the men return and break into the welding shed while Tom distracts the day shift guard. Later, George goes to a dinner party with Mary, who is keen to become more than friends. Angela doesn't like it, and her mood isn't helped when Ed cancels their date because the lead singer's walked out of his band. George gets to the Carriage Works just in time to witness another explosion. In the aftermath, he agrees to donate sperm, soon regretting it when Angela hits the roof. Pam helps George make some important decisions - but when Carriage Works owner Eric Davies eventually lets him have his rocket back, George has to consider how he can track it in space to make sure his wife's ashes go where they are supposed to.

• Kai Owen
• Robson Green
• Philip Whitchurch