The shadow lantern - Teresa Flavin

When a mysterious old oil lantern and a box of painted slides appear at Blackhope Tower, Sunni and Blaise are drawn back to the place where their adventures first began. On discovering that the slides conceal secrets about artist-magician Fausto Corvo, the pair find themselves caught up in a deadly pursuit. An old enemy is still tracking Corvo and he will stop at nothing to find him.
Sunni and Blaise must fight to protect Corvo's secrets and rid themselves of Soranzo's evil threat once and for all.The final instalment of the critically acclaimed timeslip adventure.