Demetri pretended to look at his watch, and tapped on it twice. Message acknowledged. Three seconds till action. He readied a quick levitation spell. Without words or materials, it took more effort to cast, but for one as skilled as Demetri, it was a hardly noticeable drain.
3...2...1
"Agito!" He yelled in Latin, language of the alchemists. An invisible force pushed Minerva out of her seat. She let of a sharp "Eek!" as she fell forward quickly and was caught by that same force inches from the floor.
FWISH! The cane whizzed centimeters above Minerva's head. it wasn't until the watcher was safely taken care of did he release the Darling Girl softly onto the train floor. The soft thud on the floor broke her from her fear-induced paralyzation, and she scrambled to get away from the creature above her. She scurried to the farthest corner from the living shadow, and sat there scrunched up and shivering.
The watcher writhed it's gruesome from, scratching at the cane and snarling, but to no avail. Such a creature was like an ant to Larséne, why, she practically looked bored with the shadow's efforts.
"I doubt you've noticed, but you've had two shadows since we left Welshpool's town limits. It seems you've drawn someone's attention by contacting me," he said to the still-terrified Minerva, all the while righting symbols with his finger in the air,"Don't be afraid, watcher's are useless once they've been seen. It's an early summon most alchemists learn to use as mediocre spies or house watchers that will alarm them if anything unusual happens. Larséne could probably take about 472 of these with just her cane." he said factually. This did little to comfort Minerva however. The air glowed red were his finger had touched.
"You don't happen to have any salt on you by chance?" Minerva shook her head, slightly confused. "Ah, it's no matter." He thrust his hand forward, pushing the symbols toward the creature. They stuck to the watcher's skin and began to glow.

"Potior! Verus." half the symbols began to glow green, the other half a cobalt blue. A holding sequence to keep the creature from slithering back into the darkness, not that it could get away from Larséne's cane anyways, and a truth spell to acquire the name of its master. The watcher hissed, scratching at the glowing symbols on its skin.
"If you want to go, you'll answer a few questions. Firstly, who sent you?" Demetri said, making eye contact with the shadow. "We can do this the easy way, or I can tell Larséne's to stop holding back..." The creature wiggled and flailed, motioning defeat. The bubbling form of his face began to meld, forming a more human mouth. It began to speak in demonic sounding tons.
"Skraa...I will speak. My-SRISSSS!" the creature began to contort in agony. Large orange symbols began to glow, their brightness covering the green and blue.
"Dammit!" Demetri plunged his arm into the creature and began mumbling in latin, before pulling his hand out. The creature began to glow brightly before vanishing.
"It was a high level kill spell, triggered by speaking anything of nature related to the creature's summoner or master. Demetri said, "Once triggered, it's impossible to revoke. An agonizing death to say the least, to punish treachery." he left out the fact that he had set a script to kill it painlessly instead.

((sorry that took so long ._.)