WARNING: EXTREME SPOILERS!
- Act 1 - game start.
- Act 2 - after capturing and interrogating the first alien.
- Act 3 - after assaulting the Alien Base and capturing the Hyperwave Beacon.
In order to progress in the Storyline there are certain milestones that need to be reached. The table below lists the path to completing (and winning the game). Each objective consists of a number of subobjectives that need to be completed before moving to the next.
Capture A Live Alien
|Construct the Alien Containment Facility||"An Alien Containment Facility is required to safely house an alien captive. From Engineering, select Alien Containment Facility from the list of available options to begin construction."|
|Research the Arc Thrower||"The Arc Thrower is needed to disable a potential alien captive without killing it. From the Research Labs, select Arc Thrower from the list of available research options to begin the process."|
|Build an Arc Thrower||"With the necessary research completed, return to Engineering and select Arc Thrower from the list of available items to fabricate the device."|
|Capture a Live Alien||"After equipping one or more of your soldiers with an Arc Thrower via the Soldier loadout screen in the Barracks, you can deploy and begin seeking out an alien target for capture. The Arc Thrower has a limited range, which will require our troops to get very close to the intended target."|
|Interrogate the Captive Alien||"With the alien captive retrieved from the field, we should begin the interrogation as soon as possible. From the Research Labs, select the Interrogate alien option to begin."|
Capture an Outsider Alien
|Capture an Outsider Alien||"Using an Arc Thrower, stun an Outsider alien to retrieve it for further study. Outsiders have been spotted in close proximity to UFO crash sites."|
|Research the Outsider Shard||"With the Outsider Shard retrieved, we should begin researching it immediately. From the Research Labs, select Outsider Shard from the list of available research options to begin."|
|Build the Skeleton Key||"Now that we fully understand the capabilities of the Outsider Shard, Dr. Shen can fabricate the Skeleton Key. From Engineering, select Skeleton Key from list of available build options to begin."|
Alien Base Assault
|Assault the Alien Base||"With Dr. Shen's newly developed Skeleton Key, we can now attempt to infiltrate the alien base. From Mission Control, accept the Alien Base mission."|
Trace the Hyperwave Signal
|Research the Hyperwave Beacon||"Dr. Vahlen is eager to begin studying the alien device recovered from their base. From the Research Labs, select Research Hyperwave Beacon to begin."|
|Construct the Hyperwave Relay||"After researching the Hyperwave Beacon, we'll need a facility to house the device in before we attempt to activate it. From Engineering, select the Hyperwave Relay from the list of available choices to begin construction."|
|Scan with the Hyperwave Relay||"With the Hyperwave Relay in place, we should begin scanning for new contacts from Mission Control. It's possible the relay will detect something we've missed in our previous scans."|
Intercept the Overseer UFO
|Research an Advanced Fighter Craft||"Without a more powerful jet of our own, we have little chance of shooting down the alien Overseer UFO. Select Research Advanced Fighter Craft from the Research Labs to begin developing the necessary schematics."|
|Build the Firestorm||"Having completed our research into the advanced fighter prototype, we can now begin fabricating our new jet in Engineering by selecting Build Firestorm."|
|Intercept the Overseer UFO||"We'll need to shoot down the Overseer UFO if we hope to gain access to the systems onboard that ship."|
|Assault the Crashed Overseer UFO||"With the Overseer UFO shot down, we'll need to deploy our troops to the crash site as soon as possible. From Mission Control, accept the Crash Site mission to begin the assault."|
Use the Ethereal Device
|Research the Ethereal Device||"The device recovered from the Ethereal alien species is ready for testing. From the Research Labs, select the Ethereal Device from the available options to begin the necessary research."|
|Construct the Gollop Chamber||"In order to fully test the capabilities of the Ethereal device we recovered, we'll need a specialized facility to house it in first. From Engineering, select the Gollop Chamber facility from the list of available options to begin construction."|
|Study a Psionic Alien||"We should begin studying a Psionic alien in order to gain a better understanding of these strange abilities. From the Research Labs, conduct an autopsy or interrogation on one of the Psionic alien species."|
|Build the Psi Labs Facility||"In order to begin testing our troops for any sign of psionic powers, we'll need to build the appropriate facility first. From Engineering, select the Psi Labs from the list of available options to begin construction."|
|Test Soldiers for Powers||"Having constructed the Psi-Labs, we can now begin testing our soldiers for psionic abilities. From within the Barracks, select the Psi-Labs option. You can test up to three soldiers at the same time. We'll need to continue these tests until we find a suitable candidate."|
|Increase our Soldiers' Psionic Strength||"Before a psionic soldier can use the Ethereal device, we must augment their psionic defense against whatever dangers they may encounter. Equip a psionically-gifted soldier with a suit of Psi Armor."|
* "We believe the only way we can activate the Ethereal device is by strengthing our soldier's psionic abilities by equipping the psi-armor."
|Use the Ethereal Device||"We now have a soldier powerful enough to attempt activation of the Ethereal device. Enter the Gollop Chamber and select the soldier who will attempt to use the device."|
Assault the Temple Ship
|Assault the Temple Ship||"Having located the Temple ship and identified our Volunteer, we've made all of the necessary preparations to assault the alien craft. Proceed to Mission Control and accept the final mission. The Volunteer must survive."|
My soldiers die when I go for a capture: See Arc Thrower for tips on how to capture safely. A Small Scout actually isn't the best UFO to attempt to capture an Outsider from, because it's open so the Outsider will activate from far away when he sees you. A Large Scout is much easier because it's likely you'll open a door and the Outsider will activate right in front of you.
I Can't shoot down the Overseer: The Overseer is very fast and you only have a short aerial combat window to pile the damage on. Firestorms have considerably longer time on target than conventional Interceptors. You may be able to shoot it down with an Interceptor if you pop all three consumables, but it's not reliable. In both cases you'll need Plasma Cannons.
I Can't use the Ethereal Device: After constructing the Gollop Chamber, you will be told that you do not have a soldier of strong enough psionic ability to use the Ethereal Device. The only requirement is actually that the soldier is wearing Psi Armor. If you already have someone equipped with the Psi Armor, take it off the soldier and reequip it.