Character Classes
Time Required
Chance of Discovery
Spy Failure
Fanatical Spies

In general most spies will be hired assassins,
although it is likely that some regular spies will be employed by player characters from time to time.

Most spying missions will fall into the following categories:

SIMPLE: Missions which require information regarding the general state of defenses
    and numbers of troops
    or preparations far some activity.
Simple missions require only the observations of the spy acting in a non-critical role,
    i.e. just being around as one of many individuals in the place.

DIFFICULT: Missions of this category require the spy to gain some secret information such as plans,
    maps, etc.
Difficult missions require the spy to gain access to something or gain the confidence of someone,
    and so the spy must actively pursue his or her role in an outstanding manner.

EXTRAORDINARY: Missions of long,
and hazardous nature
which require insinuation of the spy into an organization or operation
    and the relay of detailed information an a continuing basis from the spy.
Extraordinary missions require long-term association of the spy with the spied upon
    and the continuing acquisition of general and specific information of highly detailed and secret nature.

In SIMPLE missions there is little risk of discovery,
while risks become more likely in DIFFICULT missions,
and very great in EXTRAORDINARY missions.
Where a player character is involved,
    spying missions are a matter of interaction according to the dictates of the player involved,
    through the DM,
    according to the situation as known by him or her and the reactions of the spied upon.

In the case of a NPC undertaking a spying mission, a success table is used.

ASSASSIN SPYING TABLE          Chance of Success According To Category
Level Of The 
(travel + 1-8 days)
(travel + 5-40 days)
(As required)
1st 50% 30% 10%
2nd 55% 35% 15%
3rd 60% 35% 15%
4th 65% 40% 20%
5th 70% 45% 25%
6th 75% 50% 25%
7th 80% 55% 30%
8th 85% 60% 35%
9th 85% 60% 40%
10th 90% 65% 45%
11th 90% 65% 50%
12th 95% 65% 50%
13th 95% 70% 50%
14th 95% 70% 50%
15th 95% 75% 50%
16th 95% 75% 55%
17th 95% 75% 60%

Time Required To Accomplish Mission:

The length of time necessary to travel to the region in which the spying activity is to take place must be determined by the referee according to circumstances.
Once in the necessary locale, the spy will then take a variable period of time to accomplish the mission (or fail),
according to the degree of difficulty of the task:

SIMPLE: 1 to 8 days
DIFFICULT: 5 to 40 days

EXTRAORDINARY missions must be determined by the circumstances of the case.
For example,
a spy sent to become a member of a secret society might take a month to discover the recruiting requirements of the society,
and then spend one or more months making himself or herself eligible for recruitment,
and then become insinuated in the group.
Thereafter, he or she would gain simple or difficult information according to the time requirements shown,
and special information could be gained only as the individual gained more and more status within the organization through
continued membership and seemingly outstanding contribution.

Chance Of Discovery:

There always exists a chance of discovery, no matter how simple the mission.
The base chance to be discovered is a cumulative 1% per day of time spent spying,
    subject to a maximum of 10%,
    minus the level of the spy.
    Even if the latter brings chance of discovery to a negative percentage, there is always a 1% chance.
    Modifiers are dependent upon the precautions against spying taken by the spied upon.
        No Precautions = 1% chance per week
        Minimal Precautions = modified % (1% to 10%) chance per week
        Moderate Precautions = modified % chance twice per week
        Strong Precautions = double modified % chance twice per week

Minimal precautions represent occasional checks on individuals and their activities and some watch on important information.
Moderate precautions are simply more frequently carried out minimal precautions
    and more careful questioning of anyone behaving in a suspicious manner.
Strong precautions include many security checks on individuals and information,
    as well as counterspies operating to discover any such activity.

If a spy actually becomes a leader in a group,
the chance for being detected then drops to that of the category of NO PRECAUTIONS,
as the individuol is regarded as being "above suspicion",
i.e. only certain jealous or ferret-like operatives will still check on the individual.

Chance of discovery will increase tenfold if a spy is caught
and another spy is still attempting to operate during a period of 20 to 50 days thereafter.

To find if a spy is discovered, roll percentile dice according to the time period stated.
If the mission takes only a fraction of the time stated,
roll a third percentile die for tenths of percent.
Thus 1% per week equals .14% chance per day, so a roll of 99.9% indicates discovery on a 1 day mission.
If a spy is discovered, go to the SPY FAILURE TABLE below.

Spy Failure:
If, after spending the requisite time, the spy rolls and is not successful, various possibilities exist.
The results are determined on the table below.

Note that this table is also used for spy discovery, with appropriate modifiers.

Dice Score Result
01-35 Further attempts to gain success are possible, 
    but time to accomplish the mission must again be determined
36-60 Any further spying attempts will be 90% likely to result in failure, discovery, and imprisonment
61-80 Spy caught is in suspicious act, imprisoned, and nothing further is heard*
81-95 Spy is caught with positive proof of spying activity, and is tortured 
(1-2 dead, 3-4 revealed everything, 5-6 turncoat)*
96-00 Spy is killed or turns coat if counterspies are present

* If counter spies are employed they will give the spy false information and follow him or her to find where he or she come from and who sent him or her to spy in the first place.

DIFFICULT Mission = + 10% on FAILURE dice score
EXTRAORDINARY Mission = -5% on FAILURE dice score
Discovered = +25% on FAILURE dice score

Fanatical Spies:
Spies who are absolutely dedicated to their master or a cause cannot be assassins normally hired to spy,
but such can exist.
These spies will never become double agents.
On any dice total over 60 they simply kill themselves.

(Cf. EXPERT HIRELINGS for the cost of non-player character spies.)<>

"How useful can this section really be? (Reading the DMG, p.18)"
go to a city
this takes you to the overland map
choose a 1 mile square
if the spy is successful, you have access to 1 the AREA maps in that square
that's the core of the idea; the idea in it's simplest form ...

No, hiring an assassin to SPY is not an evil act.
Initiating a contract is. (cf. GHA, 0-level characters, for an alternate view of the Character Alignment Graph)
SHOP > ASSASSINATE = an evil act = -1 on a characters Morality score.