The first time he'd wiped her mind she'd begged to keep her memories, her essence, and he'd ignored her pleas, hoping to save her life by erasing the only time she'd really lived.

The second time he invaded her head she had run into him on the street, recognized his face and screamed. He vowed not to return to London during her timeline until he regenerated, taking care to avoid his mate at all costs.

This time was different. His brilliant, brave, loud Donna was ill, desperately so. His hearts nearly stopped when Wilf called and he went to her home instantly, unable to speak at the news that Donna was dying, that he needed to come say goodbye. The Doctor found his companion lying on her bed, fighting to survive the chemical coursing through her system. His own breath caught in his throat as he watched her, far too quiet, too still.

The Doctor looked at the floor and saw the cause of Donna's trouble: a small, simple bag of chocolates. He really shouldn't have left behind the candy from Halcya but she'd always loved chocolate, and they looked “normal” enough it wouldn't trip her memory. He'd just wanted to give her something after all she'd done for him. How could he know she'd be allergic?

Apparently she'd popped a couple of the sweets in her mouth and suddenly felt sick. Donna had shouted for her mum then collapsed. She'd not woken in the hour since, calling out his name while she slept fitfully, as if waiting for him to come to her.

The two men carried her to the TARDIS (Sylvia refused to help, blaming him for her daughter's predicament in the first place) and gently placed her in the med bay. Donna's condition was steadily worsening, her entire body shaking as it tried to combat the poison.

When they landed, Wilf watched over her while the Doctor left to fetch the antidote. It wasn't the easiest compound to find but after only a few minutes he returned. He hurried back into the ship, prepared to help her, but was met at the door by a sobbing Wilf. Donna was dead; she had passed away while he was out on the planet, suddenly refusing to breathe.

Donna couldn't be gone; he wouldn't allow it. The Doctor ran to the med bay, unwilling to accept that she had died, but when he rushed to her side the diagnosis was confirmed: Donna was no longer breathing, nor could he find a pulse in his friend's neck.

He placed a gentle hand to her cheek, her face terribly pale, and remembered how she'd always complained about the coldness of his fingers. Donna's skin was still warm; she'd only been dead a minute or so. He pulled out a medical kit, determined to save her. Donna had never given up on him, and he wasn't about to let her down.

He injected her with the medication and Donna suddenly gasped, coughing violently before relaxing back into the mattress, still unconscious. She had gone into anaphylactic shock, her heart and lungs seizing up, but the drug reversed the effects almost instantly. Her pulse was slowly evening out and her airway was no longer constricted; she was still alive.

They brought her home and he sat beside her for a while to make sure she was all right. “Hey, Spaceman,” Donna greeted as she awoke, her tired gaze fixing on him. “Missed you. Sort of.”

The Doctor grinned, helping her sit up. She frowned. “Am I still sick?” He took her hand, rubbing it gently with his fingers. “No, Donna,” he answered, “you're safe now.”

“Thanks.” She smiled. “Just can't leave me alone, can you?” she teased. “Nope, can't get rid of me.” He gave her a hug, checking her pulse before pulling away. “I'll always be around to take care of you, you know that.” Donna nodded.

“But I can't know, can I?” she asked sadly, a tear escaping the corner of her eye. “I'm sorry,” he said, brushing the wetness from her cheek, “but you'll be okay. We both will. I promise.” Donna squeezed his hand. “Take care of yourself, yeah?” she requested. The Doctor agreed and she settled back into the bed, permitting him to frame her face with his long fingers.

“Goodbye, Doctor,” she murmured, “and thanks again.” Her eyes closed as she forgot the last several hours, and as Donna fell asleep she felt him press a tender kiss to her forehead. “Anything for you, Donna,” the Doctor promised, then he covered her with a blanket and left.

He knew he wouldn't stop seeing her, but he desperately hoped she would never see him again.