Yng nghanol y gwanwyn, o dan planhigion gwyrddlas a blodau newydd ar wynt y mynyddoedd, stori dywyll oedd yn datblygu dan y ddaear.

In the middle of spring, under greenish plants and new flowers on the mountain winds, a dark story was unfolding underground.

Yn y cymoedd agos at y pwll glo segur, roedd dirgelwch yn symud gyda chyfres o ysgytiadau anghyffredin.

In the valleys near the idle coal pit, a mystery was moving with a series of unusual tremors.

Roedd Gethin, brwd hanesydd lleol, yn teimlo'r adrannau hanes heb eu darganfod yn galw ato.

Gethin, an enthusiastic local historian, felt the undiscovered chapters of history calling to him.

"Beth yw'r dirgelwch yma?

"What is this mystery?"

" meddai Gethin.

said Gethin.

"Mae angen i ni wybod.

"We need to know."

" Roedd ganddo ddamcaniaeth y gallai arteffactau cudd bodoli yn y dulliai islaw, ac efallai mai rhywbeth oedd yn achosi'r ysgytiadau.

He had a theory that hidden artifacts might exist in the tunnels below, and perhaps something was causing the tremors.

Gyda Rhian, daearegwr profiadol, a Tegan, newyddiadurwraig ddiddraig, fe ddechreuon nhw ymchwilio.

With Rhian, an experienced geologist, and Tegan, a curious journalist, they began investigating.

Rhian, â'i gwybodaeth fanwl o ddaeareg, oedd yn poeni am y posibilrwydd o dirlithriad peryglus.

Rhian, with her detailed knowledge of geology, was worried about the possibility of a dangerous landslide.

Ond roedd Tegan, yn anesmwyth am wirionedd dirgel a fyddai’n hwb mawr i'w gyrfa.

But Tegan, anxious for a mysterious truth that would be a major boost to her career.

Roedd gan bob un agenda eu hunain.

Each had their own agenda.

Panethodd yr haul trwy'r cwm, a Gethin oedd yn gyntaf i sylweddoli'r glud ar y muriau garw o wyneb carreg y pwll.

The sun glinted through the valley, and Gethin was the first to notice the gleam on the rough walls of the pit's stone face.

Roedd hynny'n dangos iddo fod tir tueddiadol o symud.

It showed him that the ground was prone to movement.

"Beth os ydi'r cysgodion hyn yn cuddio cyfrinach?

"What if these shadows hide a secret?"

" Golygon cyflym a ddangosodd dadansoddiad Rhian ei bod hi'n bosibl oedd hynny.

A quick analysis by Rhian showed it was possible.

Ar yr un pryd, roedd Tegan yn ystyried ei chweithiau.

At the same time, Tegan was considering her options.

Wrth iddyn nhw wibio lawr i gynteddau tywyll y pwll, gyda'i gynheiliadau pren a'r golau torllwys bob cam, cawsant eu syfrdanu gan ysgytwad sydyn.

As they hurried down into the dark corridors of the pit, with its wooden supports and dim light every step of the way, they were startled by a sudden jolt.

Roedd hynny'n ddigon i wneud i'w calonau ddal eu gwynt.

It was enough to take their breath away.

Ond yr oedd yn blys hefyd, o beidio rhoi'r gorau.

But there was also a desire not to give up.

Ar y foment gywir, ymddangosodd agoriad i siambr gudd.

At the right moment, an opening to a hidden chamber appeared.

"Dyma hi!

"There it is!"

" gwaeddodd Gethin, wrth sylwi ar arteffactau o arwyddocâd hanesyddol.

shouted Gethin, upon noticing artifacts of historical significance.

Dechreuon nhw sesiwn na darllen dim byd yn y llyfrau hanes.

They began a session neither of them had read about in history books.

Ond, yn sydyn, cafwyd tremor arall.

Suddenly, there was another tremor.

Roedd Rhian yn beirniadu eu hanghymryd o beidio sylwi ar beryglon.

Rhian criticized their neglect in not noticing the dangers.

"Rhaid i ni fynd," ymyrryd Rhian mewn brysiad.

"We must go," intervened Rhian hastily.

Ond roedd Gethin yn mawr obeithio cofnodi popeth, gyda'r cymorth Tegan.

But Gethin was determined to record everything, with Tegan's help.

Fe lwyddon nhw i ddal yr arteffactau mewn lluniau, cyn i'r siambr ddechrau dymchwel.

They managed to capture the artifacts in photographs before the chamber began to collapse.

Heb oedi, dyma nhw'n tynnu'n ôl, ddiogel o beryglon pellach.

Without hesitation, they retreated, safe from further dangers.

"Dyma'r storïau gwirioneddol," meddai Tegan.

"These are the real stories," said Tegan.

Roedd gwir ysbrydion hanes yn aros yn yr arteffactau.

The true spirits of history lingered in the artifacts.

Pan roedd yr heulwen yn disgleirio dros y pwll glo, newidiodd y tri.

As the sunshine gleamed over the coal pit, the three of them changed.

Gethin, yn agoriadol ar gyfer cydweithredu.

Gethin, open to collaboration.

Rhian, yn gweld effaith hanes ar ein hunain.

Rhian, seeing the impact of history on ourselves.

A Tegan, a ddarganfu bod stori'n fwy na sŵn, yn wirionedd i gyflwyno.

And Tegan, discovering that a story is more than noise, it is a truth to present.

Roeddent, trwy'r ymdrech drawiadol a'r pystogau cyffrous, wedi darganfod rhywbeth arbennig iawn.

Through their impressive effort and thrilling efforts, they had discovered something very special.

Roedd y gyfrinach dan y ddaear wedi dod i'r golau.

The underground secret had come to light.