First things first: this is not a Psi-Ops ripoff.
I've seen that opinion promulgated on several boards, and it's pretty much entirely false. Psi-Ops is a straight-up third-person shooter based around a combination of action and sadism; Second Sight is a third-person game that's made up of equal parts adventure, shooter, stealth, and psychological drama. About the only things that the two games have in common are a protagonist with psionic powers and the ability to throw random enemies off of very tall buildings.
Second Sight begins with its unnamed hero waking up in a prison hospital somewhere in New England, wounded, amnesiac, and telekinetic. He soon finds out that he's a parapsychologist named John Vattic, whose job used to involve proving that powers like his don't actually exist.
Six months ago, on the recommendation of a psychic named Jayne Wilde, Vattic accompanied a special forces unit called Winter Ice to Siberia. Their mission was to rescue a Russian scientist named Grienko, but soon, everything started to go wrong.
Second Sight cuts back and forth between the past and the present. In Siberia, in Vattic's flashbacks, he and Winter Ice shoot it out with Russian soldiers while trying to find Grienko. In America, in the present, a psionically powered Vattic tries to uncover extra pieces to the puzzle: his identity, his powers, and what happened to Winter Ice.
Second Sight tends to change its genre at a moment's notice. Most of the time, it's a stealth-based action game; Vattic spends more or less the entire time trying to get out of or into heavily secured locations (an asylum, a military base, a gang's neighborhood), where a careless mistake might bring endless waves of guards down on him. To evade detection, you can hug walls, peek around corners, and drop enemies with a tranquilizer dart to the back of the neck.
Vattic's powers are suited more towards this kind of action than they are to outright combat. You can use telekinesis to throw distant switches or disrupt machinery, send out an astral body to check out an area before you enter, possess soldiers to scout an area or use their security clearance, or as a last resort, cloud the minds of the people around you and become effectively invisible. Vattic's powers provide most of the adventure gaming in Second Sight, as you try to use them in new ways or figure out a method of getting their old uses to work in a certain situation.
In other stages, usually ones set in Siberia, Second Sight becomes all-out action, where Vattic has to stay alive against waves of soldiers without having access to his powers. You can use a variety of weapons, such as forty-fives, machine guns, sniper rifles, shotguns, or a tranquilizer pistol, and you'll frequently have backup from CPU allies who can really take care of themselves. When Vattic has his powers during present-day shootouts, you can use them to dispatch enemies, using waves of mental force or a Vader-esque telekinetic stranglehold, or psionically heal both himself and his allies.
This is the part where Second Sight starts to bog down, honestly; while its engine handles combat well enough, the targeting crosshair was not made for human eyes. It'll lock onto somebody's chest effectively enough, but it's got a sense of humor. You'll often aim at a crate or barrel when you really want to be aiming at the chest of the guy who just stormed into the room.
The crosshair also makes headshots difficult, if not impossible, at any distance other than point-blank range. You have to carefully move the center of the crosshair with the right thumbstick, sometimes guessing as to its real position, and it'll go back to the center if you let go. Snapping off a quick headshot is much, much harder than it has to be.
That in turn makes stealth-based missions more frustrating than they have to be, since your only silenced weapon, the tranquilizer gun, only drops an enemy if you shoot him in the head. If they take a dart to the chest or leg, they'll stay up for about twenty seconds, which is more than enough time to radio for backup and sound the alarm.
I do have to give the guards this, though: they're smart. Guards will almost always radio for backup or hit an alarm when they see you, and shooting a guy in the middle of his call for help doesn't necessarily mean that help won't come. Second Sight also lets you hide in a locker or closet if one's available, so you can wait out an alarm, but the guards will actually think to check there. If they find you, they'll haul you out by the scruff of the neck and open fire.
However, they can also be a little too smart; I lost count of the number of times a guard spotted me despite my being behind cover or invisible, or the game sounded an alarm seemingly out of nowhere. It's as though the game starts penalizing you for stealth after a certain period of time, so if you go too long without being spotted you'll get nailed for no particular reason.
Then again, I'm only complaining about these problems because I like the game. These are the kinds of issues you only start to notice after you spend eight hours or so with an action title; a wonky crosshair and hyperalert guards aren't game-breaking, but they're constant little irritations as opposed to game-breakers.
Part of the reason I played the game for as long as I did was the plotline, which is like an above-average episode of "The X-Files" turned up to eleven. Vattic comes off as a likeable but desperate man trying to uncover the truth behind an international conspiracy, despite an extraordinary amount of obstacles that've been placed in his way. The game's plot has plenty of twists, including one on the final level that suddenly makes everything in the game make a lot more sense.
The "actors" in the plot are above average for a game, with amazingly expressive polygon models and a decent cast of voice actors (although it's kind of strange that everyone in Siberia communicates with each other in Russian-accented English). It's not without its quirks, such as Winter Ice's amazingly supportive commander Starke (he says "good job!" the way other people use a comma), but as games go, it's top-notch work.
Second Sight's a little short; it should keep most players busy for about ten hours, assuming they don't use a walkthrough. It's an above-average action/stealth title, but a few quirks knock it down a couple of pegs.