Category: Comics | Previous Comic: Growth Lab 3 (GLU003) | Next Comic: Growth Lab 5 (GLU005) Release Date: 2003 | Available in: Free Gallery/Growth Lab 04 - 20th Anniversary Edition

An underground military research facility in Killian has an energy overload and all the research staff are ordered to evacuate via trams but they have to wait for a team to open the gates to the tunnels first. Watches are provided to the personnel to monitor for energy spikes and it is reported that the gates are ready for unlock. Rebecca Smith is being held in confinement and the order is given to release her and Dr. Susan Lee Hughes as part of the base evacuation.

Dr. Susan Lee Hughes chastises Rebecca Smith, blaming her for their current predicament based on the fact that Rebecca eating the chocolate candies started the spread of the growth virus. Sergeant Miller arrives and tells the ladies that it is time to leave, grabbing ahold of Rebecca who angrily shakes him off as Dr. Hughes suddenly starts to feel dizzy and feels herself growing. Dr. Hughes is in distress over her inability to control the growth and the Lab Tech preps a discharge using a decom unit which successfully shrinks Dr. Hughes. Another energy spike hits the group but Sergeant Miller is having trouble unsticking the lever. Rebecca grows rapidly while the Lab Tech hands her decom unit to Dr. Hughes to try and buy them enough time to get out of the room. Miller and the Lab Tech try to unstick the lever as Dr. Hughes attempts to manage the energy in the room. Miller starts to grow and the increase in muscle mass allows him to unstick the lever. Dr. Hughes disperses the energy so that the four of them can leave and board Tram 1. Another energy spike hits and the four of them grow again and the Lab Tech radios the other trams to leave without them.

Tram 6 and Tram Eleven signal they are ready to go but Tram 7 is left behind waiting on Officer Jones (GLU004-21). Officer Jones boards the tram but her energy monitoring watch starts acting up and Jones keeps this to herself to avoid being left behind. Tram 7 Operator notices the energy spikes and refuses to depart from the station despite protests from Office Jones who has started growing. Officer Jones continues growing and is able to force the door open to the front of the tram where Tram 7 Operator is seated. Jones snatches the energy monitoring watch off of Tram 7 Operator and she begins to grow, her breasts bursting out the front of the tram.

Tram 6 Operator A and Tram 6 Operator B are in Tram 6 heading to the surface when they pass through an energy zone. The energy dampers in the tram go offline and Tram 6 Operator B tries to get re-initialize them but it is unsuccessful. Both ladies start growing, Tram 6 Operator A tries to speed them up but they both grow out of their clothes and Tram 6 Operator A radios to the other trams that they have to turn back while Tram 6 Operator B comments that she is close to blowing her energy.

Madison Jenkins and Tram 11 Operator are in Tram 11 heading to the surface and realize that Trams Six and Seven had to turn back. Madison Jenkins notices a person up ahead and assumes it's a student trapped after the quarantine and that they must pick them up before the energy reaches them. Madison Jenkins greets the student as she gets on and the tram departs. Jenkins asks the student what her name is and she responds Naomi Furihara. Jenkins asks her how long she's been down there and Naomi responds that is been too long and starts to grow. Jenkins radios to Tram 11 Operator that Naomi is infected as Naomi grows rapidly, breaking through the ceiling of the tram. Jenkins moves to the front of the tram with the operator and a large energy spike is detected as Madison starts to grow. Tram 11 Operator tries to get the dampers online but Jenkins continues to grow, saying her breasts feel like they're full of milk. Tram 11 Operator is able to finish re-activating the dampers and shrink herself and Madison Jenkins back to normal. Naomi reappears at the entryway to the front of the tram, having shrunk as well and immediately starts willing herself to grow again, overloading the damper. By readjusting the damper Tram 11 Operator is able to briefly hold Naomi back but Naomi overloads and shorts out the damper and loses control of her growth. Jenkins grows in tandem with Naomi and Naomi urgers her to unload the energy while Tram 11 Operator who is still normal sized pleads for her not too. Tram 11 Operator starts growing and also begins to unload. Afterward we see soldiers scanning the surface of the underground lab which is in rubble from the aftermath of an explosion. The soldiers find Naomi climbing out of the rubble and go to help her.

• In 2023, ReadyArt completely redrew Growth Lab 4 to celebrate its 20th Anniversary.