You push Keira through before she has a chance to react and lock the door.

Grabbing Keira by the arm, you shove her through the open door, then slam it behind her, quickly locking the door once again. The timer starts: ten minutes until the door lock can be engaged again. Keira spins around and you see tears stream down her face as she stares through the window. You look into her eyes trying your best to ignore the sounds of Linus approaching behind you.
"Sarah?" You hear him say. "You stayed..." Slowly you turn. You have to admit, he is a sight to behold. His body ripples with muscle and every move is as graceful as it is terrifying.
"Y-Yes.." You manage, dumbly. He smiles broadly, showing his fangs. You shiver, suddenly regretting everything. And yet, you can't help but feel a not insignificant sense of arousal. Even though he appears to be walking, he approaches you with startling speed. You feel him press against you, his hard member teasing you even through the fabric of both of your clothes. He smells different, both better and worse. He stinks of sex and blood, **** and lust. Hot tears roll down your cheeks as he teases your lips apart with his, his tongue gently caressing yours. He pushes deeper, your breasts compressed against his hard chest, his abnormally long tongue questing ever closer to your throat. The he pulls back, a string of saliva linking you momentarily. He smiles, kissing a teardrop with his icy lips, and you feel your resolve fade away. He unfurls his ridiculously large member, and you quiver in excitement, quickly pulling down your pants just enough for him to access your sopping wet vagina. He lifts you and spears you, his penis pushing deeper inside of you than you ever thought possible. He slides you up and down the wall, each motion inflicting you far too much pleasure to do anything but groan. You hope that Keira is still watching. You look down at Linus and manage, with great effort, to push your breasts free from your blouse, offering them to his ravenous fangs. He gets your meaning, and leans in to suck at them with a cruel grin. You fling your head back as his fangs enter you, your lifeblood flooding into his waiting mouth. You shiver as your strength fades away, but let out one final screech as you climax, his cum coating your inside in cold semen. Then he slides you free and turns you around, his still erect penis brushing the base of your spine pleasingly. You can now look out the window and see Keira, still watching, tears streaming down her face in torrents. You smile and blow her a kiss as Linus penetrates your jugular. You sigh with satisfaction as the warmth leaves you and you sink into darkness in Linus' arms.

You awake, hungry and exhilarated, staring into Linus' eyes. He smiles and you smile back, joining for a kiss. You feel your fangs tap his and your now lengthy tongue play in the nooks of his mouth. Without looking, you know your body is amazing, and as you stand together you confirm that fact. Your breasts are round, large and firm. Your stomach, arms and legs are muscled but smooth, just like you always wanted. You brush at your wet cunt with a clawed finger.
"What about Keira my love." You say, the desire and hunger growing within you at the thought of your friend. "We need to bring her this gift." Linus nods, his face growing serious once again.
"Here." He says, stepping towards the door. "Help me with this." He puts his talons between the door and the frame, you step forward and do the same. Together you pull. It is tough but rewarding work, as the heavy metal door buckles under your now considerable strength. You giggle with delight, then, arm in arm, the two of you step into the night.