Epis­ode Num­ber: 4×05

Writ­ten by: Al Spader

Dir­ec­ted by: Jon Crew

Trans­mis­sion: 1^st June 2025

It’s begin­ning to look like the verter­on particles we detec­ted and the unusu­al veget­a­tion on the sur­face of the plan­et are con­nec­ted. The land­ing party is express­ing con­cerns that the plants may also be respons­ible for the extinc­tion of the nat­ive civilisation.

Cap­tain’s Log: Stard­ate, 9986.5

Plot: The invest­ig­a­tion into the mys­ter­i­ous plants asso­ci­ated with the worm­holes turns into a race against time to pre­vent an invasion.

The ‘A’ Plot: The land­ing party stud­ies the tangled quar­tet of plants. It seems they are grow­ing togeth­er around the newly-enlarged worm­hole, which now meas­ures a dozen cen­ti­metres across.

Jin sug­gests that detailed ana­lys­is of their DNA may provide some more inform­a­tion, and he sus­pects it may not match any­thing known in this uni­verse. Tri­cord­er ana­lys­is con­firms his sus­pi­cions, show­ing that the DNA is ret­rochir­al, coil­ing in the oppos­ite dir­ec­tion to nor­mal, and some­thing that can­not hap­pen nat­ur­ally. The loc­al microbes in the soil pos­sess nor­mal chir­al DNA.

Vale notes that a ret­rochir­al organ­ism would not be able to feed on, or provide susten­ance to, a chir­al organ­ism. Assum­ing the plants feed purely on min­er­als and sol­ar energy, then their growth is unlim­ited, but they have no nat­ur­al nat­ive pred­at­ors, which means they can eas­ily out-com­pete oth­er organ­isms. This would be dev­ast­at­ing to the eco­sys­tem, and the spread of the plants across the plan­et seems to con­firm this. Their spread off-plan­et would be extremely dan­ger­ous, so Jin imme­di­ately recom­mends decon­tam­in­a­tion pro­ced­ures should be intro­duced on their return both to the shuttle­craft and to Lyo­n­esse.

Whilst talk­ing to the ship, he asks for orbit­al scans which con­firm that a float­ing form of the plant, sim­il­ar to algae, is doing the same thing in the oceans, push­ing out the nat­ive spe­cies. In fact, there are no nat­ive anim­als or plants on the plan­et more com­plex than insects and ferns, and these are being forced into the arc­tic regions, where the plants have not spread.

The sci­ence teams con­firm that the ret­rochir­al DNA dis­covered by the land­ing party matches that of the plants dis­covered on the space sta­tion. This one seems to be sus­tain­ing itself on energy from the react­or, and its worm­hole is half-a-metre across. Hop­er­a’s board­ing party is also able to con­firm that the verter­on energy levels match those on the sur­face, although oth­er vari­et­ies of the plants pro­duce oth­er energy levels.

Cap­tain Mas­uda orders the pro­duc­tion of a tar­geted biocide, in case the plants pose a threat in their own right.

The land­ing party resumes its flight towards the nearest city, Jin not­ing that the con­di­tion of the build­ings is con­sist­ent with about two cen­tur­ies passing since it was aban­doned. The plants are every­where, and they detect a large con­cen­tra­tion in what seems to have been a park, with a cor­res­pond­ingly power­ful verter­on emis­sion. Assum­ing this is a lar­ger worm­hole, they land for a closer investigation.

It turns out that this worm­hole is large enough to send a small thruster-powered drone through. Valik and James put one togeth­er using a tri­cord­er and spare parts in the shuttle, then James remote-pilots it into the worm­hole, intend­ing to get it as far as he can. Sensor scans of the inside reveal little of the struc­ture – its length, in par­tic­u­lar, appears to vary moment by moment from 3 metres to mil­lions of kilo­metres – but it emerges into nor­mal space after trav­el­ing little more than a hun­dred metres.

The ter­minus seems to be in space, and they are able tri­an­gu­late its loc­a­tion using loc­al pulsars and oth­er sig­nal sources; it matches BC-13d, but the Black Neb­ula seems to be absent. The plan­et itself is present, and appears to be M‑class, but then they real­ise there’s a huge ring-shaped arti­fi­cial struc­ture sur­round­ing the ter­minus. Images show hun­dreds of docked space­ships, then they see some kind of weapon sys­tem tar­get the drone and des­troy it.

A quick con­fer­ence with Mas­uda on the ship, and Hop­era on the sta­tion, comes to the con­clu­sion that the plants might be some kind of weapon. Ship­board sensor scans are show­ing huge worm­holes in cir­cu­lar patches of the water­borne vari­ant at the centre of the largest ocean. These are show­ing the same read­ings, indic­at­ing they are the same species.

The land­ing party begins look­ing for a lib­rary or oth­er data store, in an attempt to find out what happened to the pop­u­la­tion, but the build­ings in the city are too dam­aged to pre­serve any­thing. The orbit­al scans show that the arc­tic regions are free of the plants, so they won­der if there are less ruined com­munit­ies there.

Trav­el­ling north, they find what appears to be an intact town, although there is no sign of life. They land to explore it, find­ing a cemetery that appears to be much lar­ger than needed for a com­munity of that size. Tri­cord­er scans show that the occu­pants were humanoid. Jin sug­gests that the people had seen the end com­ing and tried to escape to this region, before dying from the lack of food.

Fur­ther north, they find what appears to be a vault set into a moun­tain under a gla­ci­er. Think­ing that it is pos­sible there are sur­viv­ors with­in, they decide they should attempt to enter it, des­pite the Prime Dir­ect­ive implic­a­tions. Valik sets up a force-field to pre­vent con­tam­in­a­tion, then hacks into the lock mech­an­ism. There is no power to oper­ate the armoured doors, so they con­nect them to the shuttle in order to get them part­way open.

Inside, they find a long pas­sage lead­ing into the moun­tain, end­ing in a lobby area with a door to an elev­at­or, a stair­case and a shal­low spir­al ramp large enough for vehicles. Decid­ing that the elev­at­or and the stairs are prob­ably not safe, they take the ramp down, and a couple of kilo­metres later, they emerge in a domed cham­ber over five hun­dred metres across. Vale detects high­er-than-usu­al radi­ation levels, although they are still safe, and Jin notes that there were pro­pos­als to use nuc­le­ar devices for this kind of thing on Earth in the 20^th cen­tury. On the flat floor of the cham­ber, they see a num­ber of large box-like struc­tures arranged in a ring around a cent­ral cir­cu­lar build­ing. There is no sign of life.

Check­ing the struc­tures, they come to the con­clu­sion that these are ware­houses, each ded­ic­ated to the pre­ser­va­tion of a dif­fer­ent kind of cul­tur­al arte­fact: books, art, sci­entif­ic data and so on. The struc­ture in the centre appears to be a manned mon­it­or­ing facil­ity, com­plete with liv­ing quar­ters and food sup­plies, but the occu­pants appear to have died in the per­form­ance of their duty. There are sev­er­al shal­low graves in the ground out­side, and three bod­ies in the build­ing, two in beds, and one that appears to have shot them­self in the con­trol room. They have been dead for decades.

The facil­ity’s com­puter sys­tem is still powered, and Jin is soon able to get access to a data­base, detail­ing the his­tory of this civil­isa­tion’s fall.

It began with the dis­cov­ery of unusu­al plants on a remote farm, which the farm­er took to loc­al sci­ent­ists for ana­lys­is. They were unable to learn much, but the plants began to spread, occupy­ing more ter­rit­ory every month. Vari­ous teams worked with the plants, try­ing to learn more about them, then an exper­i­ment on the primary orbit­al plat­form went wrong, and all research was shut down while they tried to work out what happened.

On the sur­face, mean­while, the plants spread unchecked, crowding out the nat­ive veget­a­tion and caus­ing the star­va­tion of live­stock. Fur­ther hav­oc was wreaked at sea, as the aquat­ic plants were sim­il­arly over­whelmed, caus­ing the col­lapse of entire eco­sys­tems. Tra­di­tion­al herb­i­cides failed, and they were unable to find any­thing that could erad­ic­ate the seeds. Soon, com­munit­ies were unable to sur­vive on the food they had, and whole pop­u­la­tions began to migrate, first to the cit­ies, then to the arc­tic wastes where the plants could not survive.

But it was too late, and the pop­u­la­tion col­lapsed cata­stroph­ic­ally. The sur­viv­ors lingered on for anoth­er two dec­ades, set­ting up the vault in the hope that someone might sur­vive to redis­cov­er their culture.

There is silence for sev­er­al minutes while the officers reflect on the tragedy that befell the people of BC-13d.

They copy the data­bases and scan the art for the records, but reseal the vault in hopes that maybe a future civil­isa­tion will arrive on the plan­et and bene­fit from it.

The cap­tain decides that they should erad­ic­ate the plants, and orders the deploy­ment of the biocide. It seems this is just in time, as sensors are detect­ing a large ves­sel emer­ging from one of the ocean­ic worm­holes. As the biocide takes effect, the worm­hole col­lapses and the ali­en ship dis­ap­pears in a huge explosion.

They come to the con­clu­sion that the plants were delib­er­ately cre­ated and intro­duced as an inva­sion tool, a very long-term project.

The crew are unchar­ac­ter­ist­ic­ally quiet as they leave the dead planet.

Obser­va­tions: DNA in known organ­ic life always coils in the same dir­ec­tion, as a res­ult of the struc­ture of its con­stitu­ent molecules. The term “ret­rochir­al” is used by Jin to describe the reversed DNA dis­covered in the invas­ive plants. It is proof of their altern­ate uni­verse origin.

The under­ground arc­tic cham­ber con­tain­ing the vault appears to have been carved out by a nuc­le­ar explo­sion. Dur­ing the 20^th cen­tury on Earth, there were pro­pos­als to use nuc­le­ar explos­ives as engin­eer­ing tools under pro­grammes such as “Pro­ject Plow­share”.

Ques­tions: Who was invad­ing this world? And how did the first plant arrive?