Comic Title: House of Secrets #25
Publisher: DC (National Comics Publications, Inc.)
Address: 575 Lexington Avenue, New York, NY
Cover Date: October 1959
On Sale Date: August 20, 1959 Copyright Date August 20, 1959
Source: Library of Congress, Periodicals 1959

Frequency: Monthly
Cover Price: $0.10
Page Count: 32
Editor: Jack Schiff

Title: "The Secret of the Sea Monsters"
Pages: 8

Feature(s):
Mark Merlin (of Earth-1)

Artist: Mort Meskin

Feature Character(s)

• Mark Merlin (last appearance in House of Secrets #24; next appearance in House of Secrets #26)

Supporting Character(s)

• Elsa Magusson (last appearance in House of Secrets #24; next appearance in House of Secrets #26)

Other Character(s)

• Mr. Stevens (president of Trans-American Shipping; no further appearances)
• A race of sea monsters (no further appearances)

Synopsis:
Mr. Stevens, the president of Trans-American Shipping, contacts Mark Merlin to investigate strange attacks on his ships by sea monsters. The only damage done to the ships is the loss of their anchors. Mark dives to the ocean floor and finds a pile of worn anchors. The sea monsters are using them to dig a hole in the side of an underwater mountain.

Mark returns to the surface and informs Mr. Stevens. Stevens speculates that the creatures must be trying to enlarge the hole to allow more of the sea creatures to reach the upper world. Stevens arranges for depth charges to be dropped on the creatures. Mark dives again to place marker buoys.

While Mark is placing the buoys, the sea creatures contact him via telepathy. They explain that pressure is building in the mountain. If the gas pressure is not released, the mountain will explode and cause significant damage to the world above. Mark helps the sea creatures finish digging their hole to relieve the pressure. The gas escapes preventing the explosion and pushing the depth charges out of range. Mark thanks the sea creatures, then informs Stevens of the near disasterous mistake.