Books about Parker, Penny (Fictitious character) -- Juvenile fiction

Behind the Green Door

Guilt of the Brass Thieves

The Clock Strikes Thirteen

Ghost Beyond the Gate

Danger at the Drawbridge

Hoofbeats on the Turnpike

Clue of the Silken Ladder

The Secret Pact

Whispering Walls

Swamp Island

Saboteurs on the River

The Cry at Midnight

Signal in the Dark

Voice from the Cave

The Wishing Well