The Doctor held on for his life as The Master started to tilt the dish. He knew that he should not have trusted The Master but there was no other way to stop the universe from dying. Now he will use the CVE's to make the Earth obey him and if they do not, he will send a signal to close the CVE and restart the universal collapse.
"I won't let him win." thought The Doctor, as he crawled across the walkway of the dish as it began tilting even more. With a wrench in hand, he found the cable that was connected to the dish. If he could disconnect it, The Master wouldn't be able to use the CVE anymore. Using the wrench, he pounded it against the cable a few times to loosen it. Succeeding, he dropped the wrench and started to pull and pull on the power cable.
"Come on, come on" thought The Doctor.
He kept pulling and pulling before the cable sprang free with a flash of sparks. However, as he was pulling on the cable, he lost his balance and fell.
Thinking quickly, The Doctor held onto the cable and soon, he was dangling above the ground.
As he dangled above the ground, he began to see visions of his enemies mocking him.
The first was The Master in his decayed form saying, "A fitting end, wouldn't you say, Doctor?"
Then came a Dalek, the Captain, the Cyber-Leader, Davros, a Sontaran, and then a Zygon, each of them saying, "Doctor."
But the final one was The Black Guardian saying, "You will die, Doctor!"
The Doctor was suddenly feeling tired, but he managed to swing to one of the dish's supports, before letting go of the dangling cable. He tried to hang on, but he suddenly lost his grip and he plummeted to the ground.
His companions, Adric, Tegan, and Nyssa, who were watching the whole time, gasped as they saw their precious Doctor fall to the ground.
They quickly rushed over to their friend as he laid on the ground, dying with his eyes wide open.
"Doctor?" Nyssa asked nervously.
"Doctor?" Tegan asked as well.
Suddenly, The Doctor began to see his past companions, the ones he had traveled with since that fateful day he had regenerated into this incarnation.
He saw Sarah Jane, Harry, Brigadier Lethbridge-Stuart, Leela, K9, and Romana in her first and second incarnations. Each and every one of them asked "Doctor?" worriedly.
"Doctor? Doctor?!" Adric asked, worry in his eyes as well. The Doctor looked toward him and smiled slightly.
"It's the end," he replied, "but the moment has been prepared for."
He then reached his hand behind him. His companions looked toward where he was reaching and were surprised to see The Watcher.
"The Watcher!" Adric gasped.
The Watcher walked toward The Doctor's outstretched hand, and was suddenly absorbed into The Doctor's dying body, in a small flash of green light.
"He was The Doctor all the time!" Nyssa suddenly realized.
The Fourth Doctor took one last look at his faithful companions before he was engulfed in a white light that covered his entire body, giving it a slightly cracked appearance. As the light began to fade away, The Doctor opened his eyes and he was suddenly a young man with neck length brownish-blonde hair. The Fifth Doctor then gave his astounded companions a great, big smile and then sat up, still clothed in his predecessor's clothes.
Thus ended the life of The Fourth Doctor, and the life of The Fifth Doctor began.